C# obtain customer number

Question

In a C# 2008 application, I want to obtain the customer number from the file name as my first choice. However the customer number may be entered manually by an empployee at my company. Thus I do not see a way to obtain the customer number in this situation, do you? If so, can you tell me how to code for this situation?

An alternative is to open the excel document that contains the customer number. The customer number would be the first detail row after the header in column #7. Can you show me code on how to obtain the customer number from the excel spreadsheet?