I have situation where I am employing a custom task pane in conjunction with a command ribbon:

The task pane is correctly presented when I execute the New or Open buttons, however I need to suppress additional task pain instances when execute the Load button. The load button is just supposed to populate the existing task pane with the header content from a .csv file. This works as expected until I execute the Apply button on the task pane. The code underneath the Apply button generates a new WorkBook, and updates some range content. Now when I execute Load, a new task pane instance is presented and the .CSV header content is loaded into this task pane instead of the original. I need to prevent this 2nd task pane instance from happening. Below is the code executed by the command buttons I refer to:

From the command ribbon:

Private Async Sub btnSubstationLoad_Click(sender As Object, e As RibbonControlEventArgs) Handles btnSubstationLoad.Click

     'Load the csv file so that we can obtain the substation name
     Dim fDialog As New OpenFileDialog
     Dim path As String = Nothing

     Try

          SetTaskPaneOpen()

          If fDialog.ShowDialog() = DialogResult.OK Then
               path = fDialog.FileName
          End If

          Globals.ThisAddIn.StatusBarUpdate("Loading substation data.  Please wait...")

          Globals.ThisAddIn.LoadCSV(path)
          Globals.ThisAddIn.CsvPath = path

          Globals.ThisAddIn.SubstationName = Globals.ThisAddIn.Substations(0).Location
          Globals.ThisAddIn.SubstationAlias = Globals.ThisAddIn.Substations(0).SubAlias
          Globals.ThisAddIn.INN = Globals.ThisAddIn.Substations(0).INN
          Globals.ThisAddIn.LicenceArea = Globals.ThisAddIn.Substations(0).LicenceArea

          'Store the relevant substation alias, INN and Substation Name 
          'populate the substation detail fields with this information
          Globals.ThisAddIn.UcSpenTagManager.txtSubstationName.Text = Globals.ThisAddIn.SubstationName
          Globals.ThisAddIn.UcSpenTagManager.txtLicenceArea.Text = Globals.ThisAddIn.LicenceArea

          If Globals.ThisAddIn.SubstationType = "Secondary" Then
               Globals.ThisAddIn.UcSpenTagManager.rbSecondary.Checked = True
          End If

          If Globals.ThisAddIn.UcSpenTagManager.rbPrimary.Checked Then
               Globals.ThisAddIn.UcSpenTagManager.txtUniqueSubstationId.Text = Globals.ThisAddIn.INN
          Else
               Globals.ThisAddIn.UcSpenTagManager.txtUniqueSubstationId.Text = Globals.ThisAddIn.SubstationAlias
          End If

          'Now set the file loaded flag
          Globals.ThisAddIn.FileLoaded = True

          'Force a delay so that the user can see the change to the status bar
          Await Task.Delay(3000)

          Globals.ThisAddIn.StatusBarUpdate("Ready")

     Catch ex As Exception
          'Now set the file loaded flag
          Globals.ThisAddIn.FileLoaded = False
          Throw
     End Try


End Sub

From the Apply button on the Task Pane:

Private Sub btnApply_Click(sender As Object, e As EventArgs) Handles btnApply.Click

   Dim wb As Workbook
   Dim excelName As Excel.Name
   Dim instanceFolder As String
   Dim instanceTime As String = dtpTimeOfChange.Value.ToString(Globals.ThisAddIn.PatternTimeFormat)
   Dim filePart As String = instanceTime & "_" &
                                      Me.txtChangeReference.Text & "_" &
                                      Me.txtUniqueSubstationId.Text & "_" &
                                      _utl.SafeFileName(Me.txtSubstationName.Text, " ") & "_" &
                                      Me.txtVoltageLevel.Text

   instanceFolder = Me.txtFilePath.Text & "" &
                            instanceTime & "_" &
                            Me.txtChangeReference.Text & "_PIAttributeBatchUpdate" & "" & filePart


   'Generate the tag management folder structure underneath the specified working folder
   'if it doesn't already exist
   '<yyyyMMdd_hhmm>_<SBM Reference>_<busbar number>_<substation name>_<voltage>
   If Not Directory.Exists(instanceFolder) Then
        Directory.CreateDirectory(instanceFolder)
   End If

   Globals.ThisAddIn.InstanceFolder = instanceFolder

   'Now copy the file into place and open in Excel
   File.Copy(Globals.ThisAddIn.TemplatePath, instanceFolder & "" & filePart & ".xlsm")

   'If CSV file has been loaded then clone the file in the instance folder
   If Globals.ThisAddIn.CsvPath <> "" Then
        _utl.CloneFile(Globals.ThisAddIn.CsvPath, instanceFolder & "" & filePart & ".csv")
        'Update the csv path to the new file name so that the correct reference is delivered to the template
        Globals.ThisAddIn.CsvPath = instanceFolder & "" & filePart & ".csv"
   End If

   Dim xlb As Excel.Workbook
   Dim ws As Excel.Worksheet
   Dim rng As Excel.Range

   xlb = Globals.ThisAddIn.Application.Workbooks.Open(instanceFolder & "" & filePart & ".xlsm", True)

   If rbPrimary.Checked Then
        Globals.ThisAddIn.SubstationType = "Primary"
   Else
        Globals.ThisAddIn.SubstationType = "Secondary"
   End If

   rng = _utl.GetNamedRange("TagConvention", xlb.Names)
   rng.Value = Globals.ThisAddIn.TagConvention
   rng = _utl.GetNamedRange("SubstationType", xlb.Names)
   rng.Value = Globals.ThisAddIn.SubstationType

   'add rng updates for ExportPath, BatchPath, Voltage, License Area and 
   rng = _utl.GetNamedRange("CsvPath", xlb.Names)
   rng.Value = Globals.ThisAddIn.CsvPath
   rng = _utl.GetNamedRange("ExportPath", xlb.Names)
   rng.Value = _utl.SplitPath(Globals.ThisAddIn.ExportPath, 0)
   rng = _utl.GetNamedRange("BatchPath", xlb.Names)
   rng.Value = _utl.SplitPath(Globals.ThisAddIn.BatchPath, 0)
   rng = _utl.GetNamedRange("Voltage", xlb.Names)
   rng.Value = Globals.ThisAddIn.Voltage
   rng = _utl.GetNamedRange("LicenseArea", xlb.Names)
   rng.Value = Globals.ThisAddIn.LicenceArea

End Sub

Kind Regards
Paul.