Macro problem for absolute reference

Dear all,

After I search the macro for absolute reference in search engine for several days, I still can't get the answer why the macro for the following doesn't work

Sub Absolute()
Dim cell As Range
 
With Sheets("before macro")
 
For Each cell In Selection
If cell.HasFormula Then
cell.Formula = Application.ConvertFormula _
(cell.Formula, xlA1, xlA1, xlAbsolute)
End If
Next
End With
 
End Sub

I tried several times, the macro still doesn't work. I appreciate your reply.