Sub letter_2010(control As IRibbonControl)
However, when I click the button, I get an 'Argument not optional' error. If I make the sub definition ...(Optional control as IRibbonControl) and set a breakpoint on the MsgBox line, hovering over the 'control' object yields "control = Nothing".
I guess that the ribbon isn't passing the tag option, and I need to enable it somewhere. As much as I've searched I can't find the answer though!