Ok option one may be the best then as you say the belt may not get detected properly when spinning.
Ok first thing you will have to do is open your screenset in one of the screen designers (Screen4 or MachScreen) and change the Start button (on all pages) to a VB button. I use Screen4 so not sure how its done in MachScreen but imagine it would be the same. What you do is double click the start button and a box will pop up and you just choose the VB button option, close then save screenset. May be an idea to use Save As option and choose a name for it, especially if its the standard screen you use as if you dont then there is a chance it will get overwritten if you upgrade Mach versions in the future.
Ok once you have done that you will need to load the screen in Mach (from View menu) if you have chosen to rename the screen.
Next is go to Operator menu then Edit Button Script. You should see the Start button flashing, click on it and the editor will open, in the editor paste the script below then choose File and save and thats you almost done. The only other thing to do is go into ports and pins and set up input 2 to pin 13 port 2. If you already use that input use another and change the script to the input number you have set.
Hood
If IsActive (Input2) Then
SetOemDRO(56,1)
Sleep 500
Else
SetOemDRO(56,2)
Sleep 500
End If
DoOemButton (1000)