I came across what appears at first glance an exciting reference source covering DienBien Phu and the IndoChina War in general. Interestingly, it is a Wild Bill site using TOAW game. He has well documented OOBs for both sides in the conflict and a TOAW scenario map that I think could be translated into winSPMBT without much difficulty.
links:
Dien Bien Phu – A Fatal Gamble by Wild Bill
The TOAW scenario link:
DIEN BIEN PHU 1954 v1.1b by Karim Marc HASANIC