Repeatly Let the user enter numbers

Hi Everyone, I am trying to create a gui but having a problem. User can get two video clip and type the start frame and end frame for each clip to merge. Then when they press the merge button I asked them if they want to add more frames to merge. If they press enter I want to clean the edit text and wait for them type new frames, but the problem I could not figure out how can i pause the execution until they finish typing or press enter which means they entered all frames.

Thanks all

[Geoff Hayes]

Oguz - how does the user enter the frame numbers? In a comma-separated list, or one at a time? How does he/she indicate that they have finished entering in the frames?

Could you use a modal inputdlg to grab the information?