example: declare long CreateEnv in Win32APIDLL declare long SetCallbackSolver in Win32APIDLL (long pEnv, long pcbf, double @ pUserData) pEnv=CreateEnv() nError=0 dBestObj=1E+30 nError=SetCallbackSolver(pEnv, AddressOf MySolverCallback, dBestObj) <-- hereOr is this not possible with VFP8?