That is a great idea--it never even crossed my mind. I can't thank you enough!
I couldn't get the version in the link to work, but I did another (simpler) approach, and it works like a charm.
I dropped the following into my Page_Load event:
strJavaScript =
"//Start and stop the timer so the text boxes don't lose focus" & vbCrLf & _
"function startTimer() {" & _
" var timer = $find(""" & Timer1.ClientID & """);" & _
" timer._startTimer();" & _
"}" & _
"function stopTimer() {" & _
" var timer = $find(""" & Timer1.ClientID & """);" & _
"timer._stopTimer();" & _
"}</script>"
ClientScript.RegisterStartupScript(Me.GetType, "TimerScript", strJavaScript)
TextBox.Attributes.Add(
"onFocus", "stopTimer()")
TextBox.Attributes.Add("onBlur", "startTimer()")