Forms :: Command Button To Save Changes On The Record

I have a form named CORRES_TYP with 3 text boxes and a list box. I also have a separate table with 3 field from where the information I put in the form was saved.

In my form whenever I put information on the textbox at hit add record button, these information are saved in my table and will reflect on the listbox on my form below the textboxes. Also if I select a record in the Listbox the record I selected will apprear on the corresponding textbox in the same form.

My problem is that I have been trying to create a command button that will save and change the existing record everytime I select an item in the list box and modify the information through the textbox. Here are some infromation about my table and form:

Table name = CORRES_TYP
Field 1 = CODE (Primary key, No Duplicates)
Field 2 = DESCRIPTION
Field 3 = FOLDER

Form name = CORRES_TYP
Textbox 1 = CODE
Textbox 2 = DESCRIPTION
Textbox 3 = FOLDER
Listbox name = LIST14