Write unbound form field to table

I have a form which has an unbound text field which is a calculated filed showing a date which is x months after a separate field on the form.

I need to write this field back to a table in the database when an "add" command button is clicked.

The table is called Assets
The form is called Assets List
The text field on the form is called txtWED and needs to be written back to the table "Assets" in the field "Warranty_End_Date"

If possible can I add this as an expression on an "add" command button?

Thanks
T

Write unbound form field to table