Macro jumps into function section of another macro for no apparent reason

Dear Experts:

on the active Sheet named 'My_Results' I try to run a macro that goes like this:

Sub CleanTrim_SelectedCells()

Range("D5:D" & Range("A" & Rows.Count).End(xlUp).Row).Select

    Selection = Evaluate("if(" & Selection.Address & "="""","""",substitute(clean(trim(" & Selection.Address & ")),char(160),""""))")

End Sub

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Whenever I run the 'CleanTrim_Selected_Cells' macro (see above), the code for no apparent reason jumps into the Function section of the below macro (EnterSumFormula_MyResults). Why???
The below macro also works on the 'MyResults' Worksheet (strSheet = ActiveWorkbook.Worksheets("MyResults").Name)

If I run the 'CleanTrim_SelectedCells' macro in another workbook, everything runs fine and smoothly.

Help is much appreciated. Thank you very much in advance.

Regards, Andreas

Sub EnterSumFormula_MyResults()
    Dim rng As Range
    Dim LastRow As Long
    Dim strSheet As Variant
    Dim strFormula As Variant
    
  strSheet = ActiveWorkbook.Worksheets("MyResults").Name
     LastRow = Sheets(strSheet).Range("B" & Cells.Rows.Count).End(xlUp).Row
       strFormula = "=CountByColor('" & strSheet & "'!$B$4" & ", '" & strSheet & "'!$B$4:$B$" & LastRow & ")"
    ActiveWorkbook.Sheets("2_Auswertung").Range("B5").Formula = strFormula

End Sub

Function CountByColor(CellColor As Range, CountRange As Range)

    Application.Volatile
    Dim ICol As Integer
    Dim TCell As Range
    ICol = CellColor.Interior.ColorIndex
    For Each TCell In CountRange
        If ICol = TCell.Interior.ColorIndex Then
            CountByColor = CountByColor + 1
        End If
    Next TCell

End Function

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