EXCEL. How do i find all the rows matching the values on a different row n a different file?

I have two .xls files. One of the files has a column named "customer id" witch contains about 700 8 digit values such as 11557096. The other file has a column named "requested for" that includes about 2000 values that are the customer id plus his / her name such as 11557096 - John Doe. I would like to find all the rows on the second file that match the customer id's on from the "customer id" column on the "requested for" column.