By any chance does the control with the formatting have the same name as the field it is bound to? I think not, according to the image, but not sure. This can happen if the names are the same because Access cannot distinguish between the control and the field it's bound to. I find that reports seem to respond to cf better than continuous forms do.
I also don't get the global variable need, even after the follow up comment (which explains how it gets updated, but not why the approach is needed). I've never made a form/subform as a popup or modal either and have to wonder if that's got anything to do with it. The notion of having these forms popup style seems odd to me, and there is at least 1 form event that I know doesn't fire when it's popup & I think that's Activate. There may be others that are at play here.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.