I have a code which works for creating unique code for box packing 2 subjects book together in one box where number of books does not exceed 400. The packing must contain 2 subjects within same school and same distribution centre. It also exclude books with qty greater than 200.
Now I have to revise code for 4 subjects book & 6 subject book but the condition of packing remaining same as 400 per box and now exclude more than 100 (if 4 subjects) & exclude more than 66 (if 6 subjects).
Please help modifying the code.

    '''    
    Option Explicit
    Sub GenerateUniqueCode_Stage1()
Dim ws As Worksheet
Dim lastRow As Long
Dim distCenterCol As Range, schoolCol As Range, quantityCol As Range, subjectCol As Range, codeCol As Range
Dim boxCounter As Long
Dim prevDistCenter As String
Dim boxCode As String
Dim totalBooks As Long
Dim boxSubjects As String
Dim i As Long
' Set the worksheet
Set ws = ThisWorkbook.Sheets("Sheet1")
' Find the last row with data in column E
lastRow = ws.Cells(ws.Rows.Count, "E").End(xlUp).Row
' Set the ranges for the columns
Set distCenterCol = ws.Range("E2:E" & lastRow)
Set schoolCol = ws.Range("G2:G" & lastRow)
Set quantityCol = ws.Range("H2:H" & lastRow)
Set subjectCol = ws.Range("I2:I" & lastRow)
Set codeCol = ws.Range("K2:K" & lastRow)
' Initialize variables
boxCounter = 1
prevDistCenter = distCenterCol.Cells(2).Value
boxCode = "BOX-" & Format(boxCounter, "000")
totalBooks = 0
boxSubjects = ""
' Loop through each row in the data
Dim j As Long, schoolBooks As Long, remainingBooks As Long
Dim distCenter As String, School As String, Subject As String
For i = 1 To lastRow - 1
    distCenter = distCenterCol.Cells(i).Value
    School = schoolCol.Cells(i).Value
    Subject = subjectCol.Cells(i).Value
    remainingBooks = quantityCol.Cells(i).Value
    schoolBooks = remainingBooks
    ' Exclude schools with quantity 100 or more
    If remainingBooks >= 100 Then
        codeCol.Cells(i).Value = "Excluded"
    Else
        For j = i + 1 To lastRow
            If prevDistCenter = distCenterCol.Cells(j).Value And _
                School = schoolCol.Cells(j).Value And _
                quantityCol.Cells(j).Value < 100 Then
                schoolBooks = schoolBooks + quantityCol.Cells(j).Value
            Else
                Exit For
            End If
        Next
        ' Check if distribution center changes or adding the books exceeds the box limit
        If distCenter <> prevDistCenter Or totalBooks + schoolBooks > 300 Or _
                (InStr(1, boxSubjects, "English") = 0 And _
                InStr(1, boxSubjects, "Social & Religious Studies") = 0) Then
            ' Start a new box
            boxCounter = boxCounter + 1
            boxCode = Left(distCenter, 3) & "BOXENGSOC" & Format(boxCounter, "000")
            totalBooks = remainingBooks
            boxSubjects = Subject
        Else
            totalBooks = totalBooks + remainingBooks
            boxSubjects = boxSubjects & ", " & Subject
        End If
        ' Update the box code in column K
        codeCol.Cells(i).Value = boxCode
        ' Update the previous distribution center
        prevDistCenter = distCenter
    End If
Next i
End Sub

    '''

[![Sample][1]][1]
[1]: https://i.sstatic.net/TpKRa5mJ.png