Find existing number in another workbook
 

I am using vba code to copy data from various excel sheets to a master
(database) excel sheet. These are invoices that I track. I create the
invoices and then execute a macro to copy and paste the data to the
master sheet in the proper columns. Right now, I simply find the last
row with data and insert the new data into the next available row. I
would like to be able to check to see if the invoice number exists and
have a dialog box pop up and ask if the data should be overwritten. If
the result is yes, I would like to copy the new data over the existing
row of cells in the master sheet. I will paste my current code below.

On Error Resume Next
Workbooks.Open Filename:= _
"C:\...\Invoicing.xls"
Application.ScreenUpdating = False
ThisWorkbook.Activate
Application.Goto Reference:="Inv_Number"
Selection.Copy
Windows("Invoicing.xls").Activate
Sheets("Invoices").Select
Application.Goto Reference:="Invoice"
Selection.End(xlDown).Select
ActiveCell.Offset(1, 0).Range("A1").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone,
SkipBlanks _
:=False, Transpose:=False
ThisWorkbook.Activate
Application.Goto Reference:="Cust_No"
Application.CutCopyMode = False
Selection.Copy
Windows("Invoicing.xls").Activate
ActiveCell.Offset(0, 1).Range("A1").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone,
SkipBlanks _
:=False, Transpose:=False
ThisWorkbook.Activate
Application.Goto Reference:="Cust_Name"
Application.CutCopyMode = False
Selection.Copy
Windows("Invoicing.xls").Activate
ActiveCell.Offset(0, 1).Range("A1").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone,
SkipBlanks _
:=False, Transpose:=False

etc.

End Sub

Thanks in advance for any help with this!