Add mathematical functions to X, Y, W, H fields?

I am not sure of the best way to request a feature, so I thought I might ask a question to see if the feature would be seen as valuable to the user community. I hope this is an appropriate venue.

The feature I would like to suggest is the ability to use simple mathematical operations in the X,Y,W,H fields that determine object size and position. For instance, say my object is a rectangle at x = 100, y = 200, and is of size W = 50, and H = 75 and I would like to move it up by 73 pixels. It would be nice to not have to do the addition in my head (ok, call me lazy, but this is a simple case)... it would be nice to be able to click in the "Y" field to the right of the existing number and append +73 and then hit return and the field would automatically populate with 273.

I think the only operations allowed should be addition, subtraction, multiplication and division.

The reason I am requesting this feature is that I am doing vector based GUIs for iPhone applications and I need to make sure everything aligns pixel perfect and therefore I do a lot of calculations on object locations and sizes by pixel. This would just help me do these operations faster.