Incrementing variables

Hello,

I am fairly new to Articulate 360 and perhaps I am trying to run before I can walk. However, I would like to be able to have four text input boxes on a slide, compare their values to each of four variables (numeric). For each text box that is equal to the corresponding value I would like to increment a variable (varScore) by 5 and for each text box that is not equal to the corresponding value I would like to subtract 2 from varScore.

Two questions:

1. Can I limit the text entry to numeric (disallow letters)?

2. How do I access the part of the Trigger Wizard that allows me to "Add"? I have seen this feature on several training videos but whenever I try to do the same thing, the only operator I can use is "Set".

Any help would be gratefully received.

Thanks in advance,

Simon