Locking a question's radio buttons after attempt

I'm having an issue that may be the result of the way I have created my question processing and feedback (given that I am a newbie!). I'll try to summarzie:

• I have a multiple choice question set up with no automatic feedback built into the question itself, since I'm doing it manually

• When they click on a Submit Answer button, a series of actions occur: a variable change to 1, the Submit Answer button disappears based on if the variable is set to 1 (so they can not submit their answer again...or so I thought), the feedback based on their answer appears, and a Next button appears to they can go to the next question. I want them to only have one attempt at each question (but can attempt the whole quiz as many times as it takes).

• Everything looked like it was working alright, but it turns out that once I submit the answer, if I click on a different radio button and then click on the Next button (which isn't supposed to do anything other than go to next page), their question answer records as whatever they last selected (not what they selected initially when they clicked on Submit Answer and then saw the feedback for. Sooooo...I'm wondering if there is a way to make the radio buttons inactive after they have been selected once? I don't really want to hide them (would prefer for the user to see which option they selected). I don't want to use pop-ups to provide feedback, so that's now really an option.

I tried playing around with Process Answer and it didn't seem to make a difference...so the question is, what am I doing wrong?