I don't have VB, but the Excel-2000 VBA online help describes the 1st parameter to 'Shell' as,

"Name of the program to execute and any required arguments or command-line switches; may include directory or folder and drive."

Which seems to agree with Craig's memory

There may well be issues with running old, 16-bit, MS-DOS apps on modern, 32-bit, multitasking/multithreaded Windoze platforms - especially if they try to do cunning tricks with extended/expanded memory, direct-hardware dodgy tricks, or other "DOS extender" techniques.

BTW: Keil's command-line tools are proper 32-bit console-mode applications; perhaps it's time for an upgrade?