I have the basic system planned out. What I'm concerned with that I might be off when I convert my percentages to variables. This is what I would like the system to work.

Percentages: Sucess 50% of the time, 20% you get nothing, 20% you get interupted, and 10% of the time you get caught.

I'm using a Variable that ranges from 1 to 100.

Variable = 1-50 Sucess, Variable = 51 - 70 You get nothing, Variable = 71 - 90 Interupted, Variable = 91 -100 you get caught.

I'm not too versed on XP, but is there a random number generator that could generate such a number and then use it?

Yes there is. If you go to control variables and look under operand you can select random which will choose between the range you set. Not sure if it works well cause I never used it before.