It works similarly to linking a cell in the same worksheet.
Say A4 is the original cell; the same worksheet is linked by "=a4" in the target cell. If you want to link to a cell in another workbook, then it is "=sheet1!a4" in the target cell in the other worksheet, where sheet1 is the name of the original worksheet. Any value entered (you may want to remember to format the target if needed) in a4 would then appear in the target cell in the other worksheet.
Edited by jgweed, 24 April 2006 - 01:25 PM.