Frequently this is because the user has each file opened in a separate
instance of Excel. Try opening both files in the same Excel window.

Kim wrote:

In MS 2007 I cannot copy the contents of a cell in one workbook to a cell in
another workbook. There is no paste function when I go to the other
workbook. It seems to be a problem with 2007. Does anyone else have
this problem and is there a fix?