Update a field on a form based on it's subform

[Keith]

I have a form for inputting holidays. The main form has annual days, public
days any extra days, total days and days left.

In the middle I have a sub form which is in datasheet view. This form has a
footer that calculated totals i.e. total days used etc... This is of course
not visible as it is being viewed as a datasheet.

The main form also has a footer that is used to link back to the sub form
and bring through the values of it's footer fields (the totals).

Once I have updated a record on the sub form the footer field on the main
for updates automatically.

But I want to get the days left field on the main form to automatically
update as well. How can I do this? I have tried various events on the footer
field, but since it is being updated automatically in the background none of
them seam to work.

Anybody get any ideas?

Thanks

Keith