UASM, previously called HJWASM, is a derivative work of the JWASM well know, but defunct, Assembler (well know for people that do Assembly Language, of course).
They have their support forum at the
MASM32 forum and I have insisted with them to support the BORLAND FASTCALL Calling Convention. They did it, I deeply tested and produced a few demos for Windows available at this page
http://www.atelierweb.com/borland-calling-convention/.