autosave on changing worksheet
 

Running Office 2004.
I have created an excel main page with links to several excel
workbooks/worksheets. All the workbooks have several worksheets. Each
workbook/worksheet has a link to the main page.
What I want to be able to do is, when i have finished with a worksheet,
and i select the main page link, it automatically saves it, and when
shutting down the main page it automatically saves this as well.
Could someone tell me how to do this? i.e. if it is a macro, what do i
put in the macro?

Many thanks for your help