VBA Paste Cell value if formula contains #REF! Error - vba

Question

When sending out budget files excel files I need to first copy them to a new book then remove the sections that formulas in the document use to get their values. I do this without calculating so #REF errors appear in the formulas but the values do not #REF until i calculate.
I then want to use these #REF errors as an identifier to search for, copy the cells value (pre calculation) and paste as values so I can keep the value.
I have a solution that works below but this takes upwards of ten minutes.
Sub Value_REF2()
'Definitions
Dim lCount As Long
Dim rFoundCell As Range
Dim rng As Range
Dim cell As Range
'If Error go to Process Error function
On Error GoTo ProcError
'Remove any #REF in text first to prevent infinite loop in find below
Set rng = Range("A1:BB999") 'Range may need adjusting based on Grid
'For Loop
For Each cell In rng
If cell.Text = "#REF!" Then
cell.ClearContents
End If
Next cell
' Search for #REFs in forumlas
Set rFoundCell = Range("A1")
Do
Set rFoundCell = Cells.Find(What:="#REF", After:=rFoundCell, _
LookIn:=xlFormulas, LookAt:=xlPart, SearchOrder:=xlByRows, _
SearchDirection:=xlNext, MatchCase:=False)
'Take found cell and copy paste values
With rFoundCell
.Copy
.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks:=False, Transpose:=False
End With
Loop 'Error will occur, this will trigger ProcError function
'Process Error Function - Exit Sub
ProcError:
Exit Sub
End Sub
My next solution is below which should be much faster but i just can't work out how to make the IsError look in the actual formula rather than just the cell.
IsError(cell.Formula) does not seem to work?
Sub Value()
Dim rng As Range
Application.ScreenUpdating = False
Application.Interactive = False
Set rng = Range("A1:BB999")
With ActiveSheet
For Each cell In rng
If IsError(cell.Formula) Then
cell.Copy
cell.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks:=False, Transpose:=False
End If
Next cell
End With
Application.ScreenUpdating = True
Application.Interactive = True
End Sub
The main goal of this is to keep all formulas that do not refer to outside the budget table (like FTE calculations or subtotals and totals) and only value ones that do look outside.
Any Ideas?