Try (untested)
Code:
Dim on As String, jn As String, sm As String, pn As String
on = "Red"
jn = "Mike"
sm = "Total"
pn = "Highlife"
Debug.print "UPDATE ET SET [jn] = '" & jn & "',[on] ='" & on & "',[sm] = '" & sm & "',[pn] = "" & pn
DoCmd.RunSQL ("UPDATE ET SET [jn] = '" & jn & "',[on] ='" & on & "',[sm] = '" & sm & "',[pn] = "" & pn)
Why 2 character names?
Always do a debug print before executing action queries to ensure Access is rendering the SQL you expect. Check for errors.
Action queries can be very unforgiving.