Okay, let's visit this again.
In the PROPERTIES DIALOG of the form go to TimerInterval and put 1800000. Now the timer event will fire every 30 minutes when the form is opened. Does the code you want to run every 30 minutes take longer than a few seconds to run? If not, then don't do anything else.
If it does then in the On Timer EVENT, put Me.TimerInterval = 0 to stop the timer - the rest of your code you want to run goes in the ON TIMER event as well. At the end of that code, just before the exit of the On Timer event, put the Me.TimerInterval = 1800000 so it starts again.