Control CoronaSelectMtl with Parameter Wire

I'm currently working on a series of products that have multiple colour options. There are 5+ different materials that change when the primary colour changes, and I've set them all to use CoronaSelectMtl to save time on the change over / eliminate having to have multiple instances of the products.

If I could control CoronaSelectMtl with a parameter wire (I tried - it crashes Max, tries to connect a float to undefined) I could simply use a slider to pick the material number on ALL the CoronaSelectMtl nodes it's wired to at once!