I want to concat predefined variable with text in counter expression in azure devops yml

Using format seems to work but I wanted to know if I can concat in another way.

Format

  - name: BUILD_NUMBER
    value: $[counter(format('{0}_iis', variables['Build.SourceBranch']), 180)]

Concat (doesn’t works)

  - name: BUILD_NUMBER
    value: $[counter('$(Build.SourceBranch)_iis', 180)]