Carlos,

The MAKELPARAM macro merges two WORDs (16 bits each) in one DWORD (32 bit). This is OS syntax:

LPARAM MAKELPARAM(
    WORD wLow,
    WORD wHigh
);

And a equivalent VFP function:

FUNCTION MakeLParam(nLo, nHi)
RETURN m.nLo + m.nHi * 0x10000

Note that neither nLo nor nHi should exceed 0xffff, since they are WORDs.