I believe he wants you to put that in your Timer1_Timer event. I would also set your interval property of your timer to 1000 (1 second) or even higher so you don't kill your CPU utilization.

Also, change this line:
If DateDiff("n", CDate(OldTime), Time) = 30 Then

TO:

If DateDiff("n", CDate(OldTime), Time) => 30 Then

so in case your code misses 30 (for whatever reason) your code will still be triggered and timer reset.

HTH

Tom