Form Load and CheckChange Events at times fire and not fire.

The code below will determine a user interaction with a checkbox. At times on the form load it will execute and other times it will not execute. This throws off my flag set variable at the start of the form load.

Any suggestions on how to handle (or a more efficient way) to solve my issue?

 Private Sub chkTPCalcActive_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chkTPCalcActive.CheckedChanged
        Dim GageConfiguration As String
        If TPFormLoaded = True Then
            TPFormLoaded = False
            Exit Sub
        End If
        If Me.chkTPCalcActive.Checked = True Then
            ' If TPCalcSwitchState = True Then
            ActivateTPCalculation = True
            TPCalcSwitchState = True
            GageConfiguration = ("<@:L" & GageID & "08<GAGE,P>")
            serialCOMDiscover.WriteLine(GageConfiguration)
            System.Threading.Thread.Sleep(1000)
            'ElseIf TPCalcSwitchState = True or  Then
            'ActivateTPCalculation = False
            'GageConfiguration = ("<@:L" & GageID & "08<GAGE,P>")
            'serialCOMDiscover.WriteLine(GageConfiguration)
            'System.Threading.Thread.Sleep(1000)
            ' End If
            'TPCalcSwitchState = True
        ElseIf Me.chkTPCalcActive.Checked = False Then
            ActivateTPCalculation = True
            TPCalcSwitchState = True
            GageConfiguration = ("<@:L" & GageID & "08<GAGE,P>")
            serialCOMDiscover.WriteLine(GageConfiguration)
            System.Threading.Thread.Sleep(1000)
        End If
    End Sub