How to lock down other Form Control Checkboxes when one has been selected?

See formula below -

X TRUE =IF(N108=TRUE,90,0)
FALSE =IF(N109=TRUE,120,0)
FALSE =IF(N110=TRUE,180,0)

=SUM(P108:P110)

If more than one statement is selected as true, then I get an erroneous sum. Is it possible to lock the other check boxes down?

So the Option Button is exactly what I want. However, I've hit yet another brick wall with it. Once the option button has been chosen - I want the preselected amount to flow to another cell - however, this cell should report whichever Option Button has been selected. I can't figure it out! I've attached the worksheet - I appreciate your help!

What is the "preselected amount"? Is this the numbers next to each option button?
Which cell do you want the preselected amount to flow to? Is it E8?
What do you mean by "report whichever option button has been selected"? E2 does that.

Just looking at your sheet doesn't tell me how you intend to use it or what you want it to look like. It looks like it works fine to me. I am guessing that what you want to is very simple to implement in Excel but first I have to understand it in English

The only thing I could recommend would be getting rid of all the formulas in F2:F6 and putting this formula in E8:

=CHOOSE(E2,90,120,120,120,180)

The Choose function worked beautifully!! THANK YOU!!

You're welcome!