Not sure how you set your WaS value but here is how I did it:
SETONTRIGMOB/ATTACH/XmlValue,WaS,{RND,1,5}
I actually did two different things for the Conditional part in 2 lines: 10 & 20
10 is like this:
Condition-
GETONTRIGMOB,[ATTACHMENT,XmlValue,WaS,Value] > 0 &...