If you were using a newer version of FileMaker, you could use script trigger set on the pop up to perform a script that uses the value selected in the pop up to go to the specified layout. In 9, you'd need to place a button next to the pop up.
Your script might look like this:
Go to Layout [YourTable::PopUpField]
It would be that simple if you use a value list of actual layout names for your pop up and then use the "Layout Name by calculation" option to specify the popupfield as shown above.
If you don't use actual layout names in the popup, you can use a series of If-ElseIf steps to match specific values in the pop-up to different go to layout steps.
Thanks as always for your prompt assistance!
Good to know the functionality I was thinking is not possible in FM Pro 9. I have successfully created the pop-up and the button works by calculation (I had the value list match the layouts so it was easier).
We're hoping to upgrade to FM Pro 11 in the near future so I may re-look at this function then.
You can probably add that functunality to FM 9 by installing a plug in. I'd go with the button instead myself, but this is an option you can consider.