Sub Test()
Dim Sh As Worksheet
For Each Sh In Worksheets
With Sh.Range("C3:G20")
.Formula = "=IF(ISBLANK('F:\[Base.xls]" & Sh.Name & "'!RC),"""",""ABC"")"
.Value = .Value
End With
With Sh.Range("C23:G30")
.Formula = "=IF(ISBLANK('F:\[Base.xls]" & Sh.Name & "'!RC),"""",""ABC"")"
.Value = .Value
End With
Next
End Sub