There is a very nice capability in Pro/E that lets you change how a dimension regenerates within it's limits.. By default, all dimensions regenerate at nominal when they are created, however you can set them to upper, middle or lower as well. Go to edit/setup/dim bound. In your case , you probably want to pick middle, then select dimensions that you want to regenerate to the middle value. When you are done selecting the part will regenerate. So if you have a dimension of 10+1/-0 set to middle the geometry will measure 9.5 but the dimension will still read 10+1/-0. Notice that there is a select all option so you can easily return all dimensions to nominal (or upper/middle/lower). There is also the Dim Bound table option where you can set up a certain condition (such as MMC) and quickly return to it any time you want to study it again.
All that said, I would seriously re-examine your motives for using asymmetric tolerances. In most cases I have found you are really kidding yourself if you think manufacturing is going to intentionally make the parts to anything but the middle. There are some asymmetric manufacturing processes but they are pretty special cases. I find it better to dimension everything with symmetric tolerances and then do MMC/LMC studies to look at the fits & clearances.
One place I do use both asymmetric tolerances and the dim bound functionality is with max or min dimensions of rounds or chamfers. If I want R0.5 max on a drawing and I know the minimum cutter radius is R0.2 I will make the dimension nominal 0.5 but set the upper tol to 0 and the lower tol to .3 the set the dim bound to middle. This gives me a radius that measures 0.35 with a dimension that reads R0.5 max.