Can we make a "conditional field" based on the value of another field.

Yes, I want the value of the second field to be conditional/ determined by the value of the first field.

Do you mean that you want the value of the second field to be conditional (ie, determined by) the value of first field, or the option to fill it in (ie, if it's visible/hidden or editable/read-only)? Both are possible, it's just not very clear how you want it to work...