onComm event

Dear All
I am setting up the com parameter but i am not opening the Com port
i am waiting for ComEvReceive
but when i send the data to the com
below the event does not fires
Please can you tell me why?
Many Thanks
salih
Public Sub CommPortTest_OnComm() Handles CommPortTest.OnComm
'System.Windows.Forms.Application.DoEvents()
Dim buffer As String
'buffer = myarr.BinarySearch(myarr, "A")
Select Case CommPortTest.CommEvent

Case MSCommLib.OnCommConstants.comEvReceive
'System.Windows.Forms.Application.DoEvents()
buffer = CommPortTest.Input
TextBox1.Text += buffer
end select
end sub