The field validation expression (use by calculation)
Would be Like_Fruit = "Yes".
Then any entry is valid if "yes" is entered in the control filed, but no entry is valid if it is not. THis only catches the error after data has been entered, however.
Script Triggers would be a possible option if not for needing to do this with IWP.
You could format the field as a button to run a script where it uses go to field to put the cursor into the field only if "yes" was selected. This also requires removing the field from the layout's tab order so that users always have to click on the field in order to enter data.