Heres an example:
(first drag the timer from the toolbox onto the form)
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Timer1.Enabled = True 'enable the timer
Timer1.Interval = 30000 'set the interval to 30000 milliseconds
'which equals 30 seconds
Timer1.Start() 'start the timer
End Sub
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
SomeSub() 'use the Tick event to call the sub, Tick is raised
'when the timer reached the interval
End Sub
Private Sub SomeSub()
MessageBox.Show("Hi") 'do whatever you want here
End Sub