Alright, so I shamelessly copied your frame and ran SetBindingClick("R", "MyMacroButton") and it works.
A few more questions did arise from this:
How efficient is a list of 60x /use item if only item 60 is in the inventory? Does the Blizzard code for /use item iterate through the whole inventory for each item?
Does "RegisterForClicks("AnyDown");" check for every single button press if it was R?
How do I bind the button through the key bindings menu? I tried a bunch of different ways to get the CLICK MyMacroButton in there but I am not familiar with xml at all.
Code:
<Binding name="USEITEM" >(whatdoIwritehere?)</Binding>
One more thing I ran into is changing the loot key from shift to alt. In my bindings-cache.wtf there is a line 'modifiedclick ALT AUTOLOOTTOGGLE', but how do I do this via SetBinding or something similar?