Yes, but I am not sure why you would want to do this. Israr is correct, the datum plane does disappear, but you still have a dimension to work from that created the datum on the fly. And, did your feature not create some geometry to work from to get a ref dim?
There are different ways to look at this. The datum created on the fly, created a dimension for that feature. Show the dims for that feature and the dim used to create the datum on the fly should show up. If you don't want this to be a hard dim, edit it to be (ref_dim) or "ref_dim REF".
If you want to dimension from the placementfrom the datum on the fly. Go into insert mode after the feature that used to create the datum on the fly. Modify the feature containing the datum on the fly and create a datum plane feature offset the same distance used to create the datum on the fly. Modify both features, the one with the datum on the fly and your newly created datum plane. Add a relationship to make the newly created datum plane = to the datum on the fly dimension.
Two ways to create the ref dim while in the drawing:
1. Turn on your datums while in the drawing. Create a ref dim from the newly created datum.
2. Insert a ref dim by choosing a displayed piece of geometry and choose by menu the newly created datum plane. Pro/E knows which view to place the dim by which view you have selected the geometry from first.
Pro/E suppresses datums reated on the fly, so I can sympathize. I suppose the simplest way to create the ref dim is to redefine the sketch, create the ref dim in the sketch and then show it on the drawing.
If the feature that you are trying to dimension is create after the feature with the datum on the fly, then things get more complicated. First, if this is the case, then the datum should not be an on-the-fly datum. I forget whether or not it is possible to disassociate the datum on the fly from the feature (I don't use pro/e anymore).
If the datum on the fly must remain (modeller is a mule and "no detailer is gonna tell HIM what to do".... datum was necessarily buried for patterning purposes, etc.) then more features must be made. Make a datumn axis or another datum plane coincident with the datum on the fly. Dim to that.
If you are a programmer type, think of datums on the fly as local variables in an object or function. If they are used elsewhere, then they are really global, neh?
to NOT have the controlling datum as a hard datum may be easier for you to create- but is sloppy modeling and will reek havoc on yourself or others down the road. place a hard datum and you wont regret it.
WF3 has to fixed this once and for all. Datum on the fly is back (instead of the automatic groups in WF2) but you can unhide & reuse the datum if you want. Any datum dimensions also show up with the feature in the drawing or for pattering. I just tried it and it looks great.