Display the sum of the even numbers between two integers. Visual Basic.net

Display the sum of the even numbers between two integers. Visual Basic.net

I have a Visual Basic program that excepts two integers from the user. I
need to be able to display the sum of the even numbers between the two
integers entered by the user. If the user's entry is even, it should be
included in the sum. I am having trouble figuring out the algorithm. Thank
you in advance for any help you can give me.
Public Class frmMain
Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles
btnExit.Click
Me.Close()
End Sub
Private Sub txtFirstNum_KeyPress(sender As Object, e As KeyPressEventArgs)
Handles txtFirstNum.KeyPress
' allows the text box to accept only numbers, and the Backspace key
If (e.KeyChar < "0" OrElse e.KeyChar > "9") AndAlso
e.KeyChar <> ControlChars.Back Then
e.Handled = True
End If
End Sub
Private Sub txtSecondNum_KeyPress(sender As Object, e As
KeyPressEventArgs) Handles txtSecondNum.KeyPress
' allows numbers and Backspace only
If (e.KeyChar < "0" OrElse e.KeyChar > "9") AndAlso
e.KeyChar <> ControlChars.Back Then
e.Handled = True
End If
End Sub
Private Sub btnDisplay_Click(sender As Object, e As EventArgs) Handles
btnDisplay.Click
' display the sum of even numbers
' declarations
Dim intFirstNum As Integer
Dim intSecondNum As Integer
' convert string to number with TryParse method
Integer.TryParse(txtFirstNum.Text, intFirstNum)
Integer.TryParse(txtSecondNum.Text, intSecondNum)
' find the even numbers
If intFirstNum Mod 2 = 0 Then
ElseIf intFirstNum Mod 2 = 1 Then
End If
' add the even numbers
' display the result
End Sub
End Class