Do Loop with variable output

Hi,

I have written the code below to basically populate column C within a sheet called Source. It takes the contents of the column BH in the same sheet and appends a hypen and a number corresponding to the row.
For example: AO145-090909-1 where AO145-090909 is the contents of C, the - is appended and 1 is the row that it is present within.

The problem that I am having is around:

ActiveCell.FormulaR1C1 = "=(RC[-42]&""-""&RowCount)"

By adding the variable RowCount into this part of the code it fails. But I need to add the row count into the cell.

Sub test()

Dim Counter As Variant
Dim RowCount As Variant

    Counter = 2
    RowCount = 1
    
    Do While Counter < 101

        Sheets(Source).Select
        Range("BH" & Counter).Select
        ActiveCell.FormulaR1C1 = "=(RC[-42]&""-""&RowCount)"
        Range("BH" & Counter).Select
        Selection.Copy
        Range("S" & Counter).Select
        Selection.PasteSpecial Paste:=xlPasteValues
        Range("BH" & Counter).Delete
        Counter = Counter + 1
        RowCount = RowCount + 1

    Loop
    
End Sub

Thanks for any help, its greatly receieved.

tubbsy