@Josber, cómo que no? Sí que funciona!
Código COBOL:
01 contenido pic x(50).
01 hwnd pic s9(9) comp-5.
01 WM_SETTEXT pic s9(9) comp-5 value H"000C".
PROCEDURE DIVISION.
move "Hola Josber" to contenido
move CmText1 to COBJECT
CALL "POWERCONVTOCOM" USING COBJECT RETURNING OBJETO
invoke OBJETO "GET-hwnd" returning hwnd
call "SendMessageA" with stdcall using by value hwnd
by value WM_SETTEXT
by value 0
by reference contenido