When posting please pause and think about what you writing, what the person reading it can "see". They see nothing, so you must be fully descriptive.


Three "choices". This just makes me ask...what do you mean by three choices?


A dropdown with three possible selections?
Three radio buttons?
Three checkboxes?

In any case, you are going to have to test against whatever it is you have.

If OTHER = False (so it is NOT selected) Then
disable the textbox.

However, this is an after-the-fact situation. Depending on what the three choices are:

Test their values, and explicitly make

textbox1.enabled = False (if OTHER = false textbox1 is DISabled)
textbox1.enabled = true (if OTHER = true textbox1 is enabled)