This example shows how to reference workbooks and sheets explicitly.
Dim wbFrom As Workbook
Dim wbTo As Workbook
Dim wsFrom As Worksheet
Dim wsTo As Worksheet
Dim Str1, Str2, s1, s2, s3, s4 As String
'paths of 2 workbooks
Str1 = lblFromFilePath.Caption
Str2 = lblToFilePath.Caption
Dim WrdArray() As String
WrdArray() = Split(Str1, "\")
's1 and s2 are Workbook names
s1 = WrdArray(UBound(WrdArray()))
WrdArray() = Split(Str2, "\")
s2 = WrdArray(UBound(WrdArray()))
'Worksheet names
s3 = cboFromSheeet.Value
s4 = cboToSheet.Value
Set wbFrom = Workbooks(s1)
Set wbTo = Workbooks(s2)
Set wsFrom = wbFrom.Worksheets(s3)
Set wsTo = wbTo.Worksheets(s4)
If cboFromSheeet.Text <> "Select a Sheet" And cboToSheet.Text <> "Select a Sheet" Then
MsgBox wsFrom.Name, , "from"
MsgBox wsTo.Name, , "To"
Else
MsgBox "Please select relevant sheets from the drop down menu.", vbOKOnly, "WARNING!"
End If