Check out the DefaultValue property of fields, in the tables definition window.
To change the default in fly on the code when operating on the table through a form, do something like:
CurrentFieldValue = Forms!frmYourForm!txtYourControl
Forms!frmYourForm!txtYourControl.DefaultValue = CurrentFieldValue
You might for example add the above code to the BeforeUpdate event of the control on the form.
HTH
Steve Lewy
Solutions Developer
steve@lewycomputing.com.au
(dont cut corners or you'll go round in circles)