Option Explicit

Sub test()
Dim testrange()
Dim fillrange()
Dim theusedrange As Range
Dim firstrow As Integer, lastrow As Integer, firstcol As Integer,
lastcol As Integer
Dim i As Integer, j As Integer
Dim wks As Worksheet
Application.ScreenUpdating = False
For Each wks In ActiveWorkbook.Worksheets
wks.Activate
firstrow = ActiveSheet.UsedRange.Row
lastrow = ActiveSheet.UsedRange.Rows.Count + firstrow - 1
firstcol = ActiveSheet.UsedRange.Column
lastcol = ActiveSheet.UsedRange.Columns.Count + firstcol - 1
Set theusedrange = Range(Cells(firstrow, firstcol),
Cells(lastrow, lastcol))
ReDim testrange(firstrow To lastrow, firstcol To lastcol)
ReDim fillrange(firstrow To lastrow, firstcol To lastcol)
For i = firstrow To lastrow
For j = firstcol To lastcol
fillrange(i, j) = Cells(i, j).Formula
testrange(i, j) = Cells(i, j).Value
If Left(fillrange(i, j), 5) = "=SUM(" Then
fillrange(i, j) = testrange(i, j)
End If
Next j
Next i
theusedrange.Formula = fillrange
Set theusedrange = Nothing
Next wks
Application.ScreenUpdating = True
End Sub