@excelledsoftware: Thank you so much! This will do the trick, I think.

@JohnWilson: The reason for the (control as IRibbonControl) is that ultimately I'm going to make this an add-in after I get the macro itself working correctly. As to your other question, I haven't yet decided whether I want it to work from Insert Textbox or from placeholder; I'll get to that in a bit.

Thanks again to both of you!