ltrim(rtrim(SUBSTRING([filename], charindex('Invoice', [filename])+8, LEN([filename]) - (CHARINDEX('Invoice', [filename])+11))))

[p]This snippet pulls out the invoice number from a filename. The filename is in a consistent format "MyCustomerName_Invoice_12345678.pdf". The snippet above uses the word "Invoice" as the anchor to get the invoice number and it doesn't care what the file extension is. You could use a CASE statement to test for a TXT or CSV extension. You could also use CASE to test for any consistent part of the filename. This is a T-SQL snippet so I don't know if this going to help you out of the box, but for what it's worth...[/p]