Is it possible to assign a material's thickness using an external interface?

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I've been using the external interface PtolemyServer to assign schedules for window shading. What I'd like to be able to do is use PtolemyServer to assign the thickness of materials. Is this possible? I tried changing the thickness of an object in the "Material" class to the name of a schedule or variable, but it seems like it can only accept numeric values (at least in the IDFeditor).