Enter event triggered for more than one listbox

[Twotone]

I am using Office 2003 and have created an Outlook form which has two
listboxes on it. I am trying to use the "on enter" event to do somethings
automatically when the user clicks in one of the listboxes.

The problem is as follows. When the user clicks in a listbox, the code for
that event runs correctly. However, immediately afterwards, the "on enter"
code for the other listbox runs as well. There is no "on error" event or
other code connecting these two procedures, so it seems that clicking in the
first listbox is triggering the "on enter" event of the second listbox.

Hope that's clear. I'm not really a programmer. Any ideas gratefully received.

Thanks