Hi!
At the end I came with "not so bad solution" I enhanced the PRICING model via AET with a time stamp field, this field will record the last time the price was determined via MASS, soooooo, yeah, yeah, I know.... I'm storing dummy information, but at least storing a date+time can be usefull in a future.
The other step is make the field avaliable in the Web UI part (customizing, web ui development), instead of using the field directly in the Web UI I mask it as a check box with a description "Only redetermine pricing" so the user doesn't need to modify process related info to force the pricing redetermination.
You can find further information about mass in my blog:
Cheers!
Luis