Runtime Error 13 - Mismatch - excel

Question

I'm new at VBA coding and working on a match code. The code is working just fine when I run the code in "Data sheet" (the sheet were all my data is and were the match has to be found), but when i'm run the code on the frontpage (Sheet 1 with userforms) the code is debuggen and says "Runtime Error 13". Can anybody tell what the problem is?
And can anybody tell me why my "If isError" doesn't work?
Thanks in advance!
Br
'Find SKU and Test number
Dim icol As Integer
Sheet13.Range("XFD2") = UserForm2.ComboBox1.Value 'Sættes = ComboBox1.value
Sheet13.Range("XFD3") = UserForm2.ComboBox2.Value 'Sættes = ComboBox2.value
icol = [Sheet13.MATCH(XFD2&XFD3,A:A&Q:Q,0)] 'Match af værdien for vores SKU og test nr
With ThisWorkbook.Worksheets("Data sheet")
'If SKU or Test number not found, then messagebox
If IsError("A:A") Then MsgBox "SKU not found": Exit Sub
If IsError("Q:Q") Then MsgBox "Test number not found": Exit Sub
'Add test result/next step and comment
.Cells(icol, 30).Value = Me.ComboBox3.Value
.Cells(icol, 30 + 1).Value = Me.Comments_To_Result.Value
End With
End If
Set objFSO = Nothing
Set openDialog = Nothing
Range("XFD2").Clear
Range("XFD3").Clear

Answer 1

icol should be like this:
icol = Application.match(arg1, arg2, arg3)
See the samples in MSDN:
var = Application.Match(Cells(iRow, 1).Value, Worksheets(iSheet).Columns(1), 0)
Concerning If IsError("A:A") Then MsgBox "SKU not found": Exit Sub, you are doing it wrongly. I assume, that you want to loop through all the cells in the first column and to get whether one of them is an error. You need a loop for this. This is a really simple one, but you should implement it somehow in your code:
Option Explicit
Public Sub TestMe()
Dim rng As Range
For Each rng In Range("A:A")
If IsError(rng) Then Debug.Print rng.Address
Next rng
End Sub