Say you have a source workbook, sourcelink.xls, and a destination workbook, destlink.xls. Then in the destination workbook you would put a formula such as:
=[sourcelink.xls]Sheet1!$A1
If both workbooks are open dest will immediately reflect the changes made in source.
if you open source alone and make changes then close it and open dest you will get a dialog requesting to update from source.
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