Make “read only” only one value into a check box

[robertop85194415]

As the title. I have a dropdown list with two choices that have an effect on a checkbox with 6 values. The firts value of the list makes read only all the checkbox, and this is not a problem. But I would like that the second value of the list makes read only just one value of the checkbox (the fifth). How can I do this? Thanks

[robertop85194415]

Sorry, not checkbox, radiobuttons

[try67 · Accepted solution]

If they are in the same group it's not possible.