Try this.
Private Sub SubmitButton_Click()

'Validating that the user is sure they woud like to submit

Dim Answer As Integer

Answer = MsgBox("Are you sure you are ready submit the data?", vbYesNo + vbQuestion, "Submit New Entry")

'Transfer data into the worksheet

Dim emptyRow As Long

Sheet1.Activate

emptyRow = WorksheetFunction.CountA(Range("A:A")) + 5

If Answer = vbYes Then

    Cells(emptyRow, 1).Value = TradingNameText.Value
    If licencetext.Value = True Then Cells(emptyRow, 2).Value = "FB" & licencetext.Value
    If licencetext.Value = False Then
        For Each cl In Range("B6", Range("B" & Rows.Count).End(xlUp))
            If cl.Value <> vbNullString Then
                mymax = Application.Max(mymax, ExtractNumber2(cl.Value))
            End If
        Next
        Cells(emptyRow, 2).Value = "FB" & mymax + 1
    End If
Else
'do nothing
End If

Unload Me

End Sub

Function ExtractNumber2(rC As String) As Long
    With CreateObject("VBSCRIPT.REGEXP")
        .Pattern = "[^0-9]"
        .Global = True
        .IgnoreCase = True
        ExtractNumber2 = .Replace(rC, "")
    End With
End Function