"Leith Ross" wrote:

Hello Ben,

You need to add the Solver reference library to VBA in order to expose
Solver's VBA interface.

I did add the ref library, but never explicitly hit Alt-S to save (did you
mean Ctrl-S or is the VBA interface different?).

Since making my original post, the problem has become intermittent. I
haven't yet figured out what makes it sometimes work and sometimes not. It
seems to be affected by whether/how I run the GUI Solver before trying the
VBA-launched Solver. Do you see anything suspicious in my code?

Thanks for the reference tip, and I'll post again if I can isolate the cause.