calling 32 bit exe from 64 bit app

I have a C# windows appA (exe) that is built with 'any CPU'.

In the same application folder I have another C# windows appB (exe) that is built for 'x86' that I want to run as a 32 bit.

I have dll's built as 'any CPU' that are referenced by both.

On a 64 bit machine appA starts a new process and calls appB, but instead of running as a 32 bit process, appB runs as a 64 bit process.

My question is how do I force the appB exe to be run as a 32 bit process.

Thanks,

Rick

Rick