Hello, It looks like your code is working correctly. So if you want to use a different field than description, you just have to change your code to use a different field.
For example I took your code and made it run for the fax field on the Accounts form.
We need the logical name of the field.

And then we just change the code slightly.
function showConfirmDialog() {
Xrm.Utility.confirmDialog("Click Yes or No to set the Personal Notes Value",
function() {
Xrm.Page.getAttribute("fax").setValue("Yes Callback fired");
},
function() {
Xrm.Page.getAttribute("fax").setValue("No Callback fired");
});
}

Hope this helps.