Dropdown field - when certain entries are selected make another field unavailable for data input

Question

Hi All,
Sorry one again I am very new to forms and have another question. I have a dropdown list which when selecting certain values I need another field to be unavailable so the user can't enter data.
Hope this example makes sense:
DropDown
Field %
Outer
Not Allowed to enter data
Back
Not Allowed to enter data
Inner
Not Allowed to enter data
Cotton
Allowed to enter data
Wool
Allowed to enter data
If someone could give me some examples that would be a great help.
Many Thanks
Adam Sadler

Answer 1

Here's a script that you can use for the custom Validate script of the dropdown. It resets the value of the corresponding text field whenever a change is made to the dropdown. You can get rid of the line that does this if you don't want this to happen. Change "text1" in the code to match the name of the text field you're using.
// Custom Validate script for dropdown
(function () {
    // Get the selected value
    var v = event.value;
    // Set up an object to associate read-only status of text field with items
    var f_state = {
        "Outer": true,
        "Back": true,
        "Inner": true,
        "Cotton": false,
        "Wool": false
    // Get a reference to the text field
    var f = getField("text1");
    // Clear the text field
    f.value = "";
    // Set the read-only status of the text field based on what's selected
    if (v in f_state) {
        f.readonly = f_state[v];