I'm not sure I understand your question. Are you trying to avoid the manual (math) calculation of the coordinate difrerence?
You can use the 'search relative' "SR" command to move to relative coordinates instead of absolute coordinates.
This might be a good application for reuse if you are talking about making multiple 'channels' have identical layouts.
I've used a script in the past to do place components relative to other components (before I had a reuse license).
PADS has a very useful but underused command: Setup > Set Origin. It's usually used once to set the board origin, but it is extremely useful for many different tasks too. In your case, select U1, then invoke Set Origin, and it will prompt you to use the ICs origin as the new system origin, or let you manually select another point. Choose yes, and now any other parts' coordinates will be relative to U1. You can now use the SR commands, or just select the part's properties and type in the coordinates. Just remember to set the origin back to the board origin before post processing.