Queries :: Update Multiple Table Records With Button Click Event

I have a table with many records, using a form with an update button click event, I would like to update ALL records where the Item in the table = the Item in the form.

There are 6 checkboxes and 6 text boxes that will need to be updated, but right now I am just trying to test if i can even change one text box to keep it simple. I have tried to start by using this:

Code:
Dim mySQL As String
Dim ItemNo As String
Dim SO As String

mySQL = "UPDATE BT200 SET Part = '" & SO & "' WHERE Item = " & ItemNo
DoCmd.RunSQL mySQL

So every time i run this command button, it gives me a prompt "You are about to update 0 row(s)". Nothing gets updated at all, I am clearly missing something vital here.