Smart way to have advantages/disadvantage rolls (sometimes)

Hey, So Im making a sheet where you have a normal roll, but then you should be able to turn advantage or disadvantage rolls on. I was thinking of making the way you turn it off or on as an dropdown menu, but cant get the good idea on how to code it into the rolls. The only way I can figure out is to make the value control what is shown via CSS, and so make 3 roll buttons for each roll (normal, advantage and disadvantage) Would love if anyone had a better solution :D 

I imagine you could do this by having an attribute in your macro instead of a dice roll (in the roll button).  It could be something like @{dicetype}.  Then you make a drop down menu that fills in attr_dicetype with 1d20, 2d20kl1, or 2d20kh1.  Then your @{dicetype} would be resolved into one of those and rolled when the roll button is clicked and the macro is processed.

I didnt know you could do the kl1 and kh1, so this was what i needed!  Thanks alot :D