1. I use a simple macro like this:
#showtooltip Heavy Windwool Bandage
/use Heavy Windwool Bandage
Bind that to a key and you are good to go. The advantage of this method is it works with healbot's frames, it works with blizzard's default frames, and it works if you just putt your mouse over the person or their nameplate and hit the key you have it bound to.
2. You can also do it directly with healbot so that mouse clicking on the healbot frames uses a bandage. But you do NOT need a macro for this. Go to healbot / options / spells. Choose left click, middle or right click. Delete whatever spell is on the line and type in the name of the bandage. Suppose you choose middle click. Then when you mouse over a healbot frame and middle click, it will bandage that person. You are clicking the frame, of course, but you don't have to hit anything with your left hand.
I use this second method on almost all my dps and tanks. Healbot gives you the opportunity to do three things to yourself with mouse clicks, right hand only. I usually use this function for something like a paladin shield.
p.s. if you use this second method as dps or tank, be sure to set up a healbot profile that doesn't give you everyone's healing bars, just you and maybe a pet or the tank.
p.p.s. You can put all kinds of things into healbots spell lines, potions, bandages, etc., not just spells.