Dear Muddassir,
Regarding your approach, DLL_ProcName must be the name of the SUBROUTINE called by FAST, which in this case is “DISCON”, so, change “FAST” to “DISCON”.
Regarding an error that the DLL could not be loaded, see the following topic on our forum: "DISCON.dll could not be loaded" - #2 by Bonnie.Jonkman.
Best regards,