You can rip your Cd's to ISO's using most commercial CD-Burning software (i.e. Nero) or with a program like UltraISO. You can then use Daemon-Tools to mount these images (
www.daemon-tools.cc). Daemon-Tools will take an ISO file (an image of the CD) and create a "virtual" CD drive to "insert" the CD into, thus fooling the game that there is a CD in the drive.
Daemon-Tools has a command line interface for mounting specific images which, I believe, you can put the commands into the GameEx configuration ini to mount the specific image for the selected game.
For Example: "C:\Program Files\D-Tools\daemon.exe" -mount 0,"%1"
"C:\Program Files\D-Tools\daemon.exe" - being the executable for Daemon-Tools
-mount - the operator to mount a drive
0 - the number of the drive to mount to (Daemon-Tools allows the creation of multiple virtual drives)
%1 - the name of the image that you wish to mount
I know there are tools other than Daemon-Tools for image mounting but I have found this to be the easiest and it is the only one I know how to use from the command-line which would be theonly way to make GameEx mount the images that you need at run-time.
I hope that all made sense! I haven't actually tried this method myself but it should work in theory.
(and yes, Daemon-Tools is free)

This is actually a preferred way to No-CD cracks because it does not modify the main executable which can lead to memory leaks, trojans and other like things that you do not want.
Legal Disclaimer: You can only make images of Cd's that you actually own for archiving purposes!