Applying random material to Curtain Wall panel

Revit
1

I’m trying to apply 1 of 3 materials randomly to a curtain wall panel. I can get as far as randomising 3x materials but I get an error setting the parameter and not sure what I’m doing wrong. Hoping someone can help?

Randomise%20Material%20Finish%20of%20Panel
Randomise Material Finish of Panel.png3354×790 194 KB

2

I figured it out after searching harder. If this can be improved I would be glad to hear.

Randomise%20Material%20Finish%20of%20Panel_Final
Randomise Material Finish of Panel_Final.png3336×1092 184 KB