Multiple display support-Win9x DOS mode

I have a client who needs to support an external monitor from his Dell Inspiron laptop. He is running a specailty software which runs in the DOS mode in Win 9x. The BIOS/Setup is set to SIMUL video mode to support the LCD and external CRT SIMULtaneously. The software vendor says it is a system problem, not the software. (So what’s new?) Can Win 9x support multiple displays in its DOS mode? Will appreciate relevant suggestions. Thanks.