Programmatic material swapping

Is there an interface so that I can do material swapping through an external program on a PC?

I have a tablet that is used to control other settings, and I want to use this as a way to swap materials. The tablet connects over wifi to a c# program on the PC. This c# program is what launches the Unreal environment (packaged into an executable).

I know I can create a gui in my Unreal project that can do that swapping, but the only user input I have is the tablet, so I need a way to programmatically tell Unreal to swap material, through an API call, or something similar.

Is this possible?