Setting up a combination of keyboard and mouse commands... cant work it out!

hi guys, i'm new to bettertouchtool and absolutely love it but there is one command I just can't get setup.

I want to tell my mac that when I hold down the windows key on my windows keyboard (which I believe is the equivalent of the option key) and use my scroll mouse, for it to copy the behaviour that is performed in my app when holding down the alt key (cmd key) and scroll the mouse.

Basically what I do by holding cmd and scrolling, I want to be able to do when I hold option and scroll, however because I'm using both keyboard and mouse buttons I can't see a way of setting this up.

Any help very much appreciated!