You can use conditional formatting to do this.
In design view
== Click on the control
== Select Conditional Formatting from the format menu
== Change Field Value Is to Field has Focus
== Click on the Paint Bucket and choose a back color
== Click OK
If you need to do multiple controls, then you can click on the control you
have just set up and then double-click on the format painter button (paint
brush icon) in Access 2003 and earlier. This will copy the format for the
control and stay active until you click on the Format Painter button again.
Now click on each control that you want to have the conditional formatting you
have just set up.
John Spencer
Access MVP 2002-2005, 2007-2009
The Hilltop Institute
University of Maryland Baltimore County