See if this information from Excel (2003) Help doesn't help you out:
Set a link to another program to be updated automatically

On the Edit menu, click Links.
The Links command is unavailable if your file does not contain linked
information.

In the Source list, click the linked object you want to update. An A in the
Update column means the link is automatic, and a M in the Update column means
the link is set to Manual update.
To select multiple linked objects, hold down CTRL and click each linked
object.

To select all linked objects, press CTRL+A.

To update a linked object every time you open the file that contains the
object or any time the original information changes while the file is open,
click Automatic.
Click OK.
On the Tools menu, click Options, and then click the Calculation tab.
Make sure the Update remote references check box is selected.

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I searched for phrase "auto update links" to find this, topic title ended up
being
"control when links are updated"

Hope this helps some.