The following code will return the current logged in username. Put the code into a prg and call it something like GetNetUser.

LOCAL  lpUserIDBuffer, nBufferSize, RetVal

RetVal         = 0
lpUserIDBuffer = SPACE(25) && Return buffer for user ID string
nBufferSize    = 25        && Size of user ID return buffer

DECLARE INTEGER GetUserName IN Win32API AS GetName ;
   STRING  @lpUserIDBuffer, ;
   INTEGER @nBufferSize

RetVal = GetName(@lpUserIDBuffer, @nBufferSize)

RETURN LEFT(lpUserIDBuffer,nBufferSize-1)