Mismatch error in VBA - problems with columns - excel

Question

I have a workbook where I want to find the differences of two sheets by looking at the company name and their corporate registration number and then type the differences on the third sheet.
I have tried the code in another workbook with only 143 rows, which works perfectly, but when I try it on the real workbook with 10,000 rows I get a "type mismatch error". Also if I use other columns than the CVR and Firm columns the code also works.
The CVR is numbers and Firms are strings (firm names). I get the
type mismatch error
on the line I marked **. Does somebody know why I get this error?
Sub ComCVR()
Dim CVR1()
Dim CVR2()
Dim Firm1()
Dim Firm2()
Dim n As Long, m As Long
Dim i As Double, j As Double
Dim intCurRow1 As Integer, intCurRow2 As Integer
Dim rng As Range, rng1 As Range
Set rng = ThisWorkbook.Sheets("Last month").Range("A11")
Set rng1 = ThisWorkbook.Sheets("Current month").Range("A11")
n = rng.CurrentRegion.Rows.Count
m = rng1.CurrentRegion.Rows.Count
ReDim CVR1(n)
ReDim Firm1(n)
ReDim CVR2(m)
ReDim Firm2(m)
ThisWorkbook.Sheets("CVR").Range("A1") = "Flyttet CVR"
ThisWorkbook.Sheets("CVR").Range("B1") = "Flyttet Firmanavn"
ThisWorkbook.Sheets("CVR").Range("A1:B1").Interior.ColorIndex = 3
ThisWorkbook.Sheets("CVR").Range("C1") = "Nye CVR"
ThisWorkbook.Sheets("CVR").Range("D1") = "Nye Firmanavn"
ThisWorkbook.Sheets("CVR").Range("C1:D1").Interior.ColorIndex = 4
ThisWorkbook.Sheets("CVR").Range("A1:D1").Font.Bold = True
' Inset data to arrays
For i = 0 To n
CVR1(i) = ThisWorkbook.Sheets("Last month").Cells(12 + i, 5)
Firm1(i) = ThisWorkbook.Sheets("Last month").Cells(12 + i, 4)
Next
For i = 0 To m
CVR2(i) = ThisWorkbook.Sheets("Current month").Cells(12 + i, 5)
Firm2(i) = ThisWorkbook.Sheets("Current month").Cells(12 + i, 4)
Next
intCurRow1 = 2
intCurRow2 = 2
'Old
For i = 0 To n
For j = 0 To m
If Firm1(i) = ThisWorkbook.Sheets("Current month").Cells(12 + j, 4) Then '** Error raised here
Exit For
End If
If j = m Then
ThisWorkbook.Sheets("CVR").Cells(intCurRow1, 1) = CVR1(i)
ThisWorkbook.Sheets("CVR").Cells(intCurRow1, 2) = Firm1(i)
intCurRow1 = intCurRow1 + 1
End If
Next j
Next i
'new
For i = 0 To m
For j = 0 To n
If Firm2(i) = ThisWorkbook.Sheets("Last month").Cells(12 + j, 4) Then
Exit For
End If
If j = n Then
ThisWorkbook.Sheets("CVR").Cells(intCurRow2, 3) = CVR2(i)
ThisWorkbook.Sheets("CVR").Cells(intCurRow2, 4) = Firm2(i)
intCurRow2 = intCurRow2 + 1
End If
Next j
Next i
Columns("A:B").Select
ActiveSheet.Range("$A:$B").RemoveDuplicates Columns:=1, Header:=xlNo
Application.DisplayAlerts = False
Columns("C:D").Select
ActiveSheet.Range("$C:$D").RemoveDuplicates Columns:=1, Header:=xlNo
Application.DisplayAlerts = False
End Sub

Answer 1

Whenever an error happens, the best way is to google it. This is what it says in the documentation of VBA for Type mismatch:
Cause: The variable or property isn't of the correct type. For example, a variable that requires an integer value can't accept a string value unless the whole string can be recognized as an integer.
In the case of the code, it happens, when an array is compared with excel cell. Now the trick - in order to see why it happens, see what is in these:
Debug.Print ThisWorkbook.Sheets("Last month").Cells(12 + i, 4)
Debug.Print Firm1(i)
and the after the error runs, take a look at the immediate window (Ctrl+G). It it quite possible, that there is an error in the excel cell, thus it cannot be compared. This is some easy way to avoid it, if this is the case:
Sub TestMe()
Dim myRange As Range
Set myRange = Worksheets(1).Cells(1, 1)
myRange.Formula = "=0/0"
If Not IsError(myRange) Then
Debug.Print CBool(myRange = 2)
Else
Debug.Print myRange.Address; " is error!"
End If
End Sub