Before allowing the user to actually perform the install, check for "in-use" files by using SB's handy "Check In-use Folder Tree.." that is under the "General Installer Functions" category in the script builder.
I put a call to the function in a LOOP, like this:
- display wait dialog with msg about checking for in-use files
- call the SB function to check for in-use files
- close wait dialog
- check return value of the "in-use" call
- if return value = "1" display in msg box and ask user if they want to exit install or try again. If they want to try again, repeat the loop.