Static NAT problem at an ASA

That is difficult to do. In the PIX 6.x series, it was not possible without additional external hardware. I believe it isn't possible in PIX/ASA 7.0 either. There was an intra-interface access enhancement in either 7.2 or 7.1 that -might- have made it possible.

Usually the best thing to do is to have the internal users access by host -name-, and arrange so that when they are inside the network, the host name resolves to the internal IP, and outside, the host name resolves to the external IP.