Calculations Using multiple Texas Boxes in VB.net

I am trying to do baic subtraction using texbox21.text - texbox60.text = output to Label1. The math and function works.

This is for multiple rows of the same kind of equation but with different texboxes,
Simple math. But if the values are blank I get an exception Error. Here is my code please enlighten me on what I am missing.

Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        Dim Net1 As Double
        Dim Net2 As Double
        Dim Loaded1 As Double
        Dim End1 As Double
        Loaded1 = Double.Parse(TextBox21.Text)
        End1 = Double.Parse(TextBox60.Text)
        Dim Loaded2 As Double
        Dim End2 As Double
        
        If TextBox21.Text And TextBox60.Text = False Then
            Net1 = False
        End If

        If TextBox21.Text And TextBox60.Text = True Then
            Loaded1 = Double.Parse(TextBox21.Text)
            End1 = Double.Parse(TextBox60.Text)
            Net1 = Loaded1 - End1
            Label2.Text = Net1.ToString
        End If
    End Sub

Tags: Visual Basic