How to add/minus multiple checkbox values - vb.net

Question

I'm using VB.net and I'm having trouble trying to add different values when I select checkboxes and diplaying the total in a textbox. When unchecking them, it should be subtracting the values. Here is my code
"totals" is my textbox
Dim total As Double
Private Sub cchstk_CheckStateChanged(sender As Object, e As EventArgs) Handles cchstk.CheckStateChanged
If (cchstk.Checked = True) Then
total = total + 109.99
totals.Text = Double.Parse(total)
ElseIf (chstk.Checked = False) Then
total = total - 109.99
totals.Text = Double.Parse(total)
End If
End Sub
Private Sub cms_CheckStateChanged(sender As Object, e As EventArgs) Handles cms.CheckStateChanged
If (cms.Checked = True) Then
total = total + 79.99
totals.Text = Double.Parse(total)
ElseIf (chstk.Checked = False) Then
total = total - 79.99
totals.Text = Double.Parse(total)
End If
End Sub
Private Sub prrdg_CheckStateChanged(sender As Object, e As EventArgs) Handles prrdg.CheckStateChanged
If (prrdg.Checked = True) Then
total = total + 49.99
totals.Text = Double.Parse(total)
ElseIf (chstk.Checked = False) Then
total = total - 49.99
totals.Text = Double.Parse(total)
End If
End Sub
Private Sub gb_CheckStateChanged(sender As Object, e As EventArgs) Handles gb.CheckStateChanged
If (gb.Checked = True) Then
total = total + 29.99
totals.Text = Double.Parse(total)
ElseIf (chstk.Checked = False) Then
total = total - 29.99
totals.Text = Double.Parse(total)
End If
End Sub
Private Sub nd_CheckStateChanged(sender As Object, e As EventArgs) Handles nd.CheckStateChanged
If (nd.Checked = True) Then
total = total + 29.99
totals.Text = Double.Parse(total)
ElseIf (chstk.Checked = False) Then
total = total - 29.99
totals.Text = Double.Parse(total)
End If
End Sub`

Answer 1

you only have to change all your Double.Parse(total) to total.ToString
you want to convert a number to string, not a number to a number.
also do not use double if you can, you will be hit by floating conversion issue
use decimal and you can also create a method to reduce the repetition of code
Dim total As Decimal
Private Sub ChangeValue(add As Boolean, value As Decimal)
total += If(add, value, -value)
TextBox1.Text = total.ToString
End Sub
Private Sub CheckBox1_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox1.CheckedChanged
ChangeValue(DirectCast(sender, CheckBox).Checked, 109.99D)
End Sub
Private Sub CheckBox2_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox2.CheckedChanged
ChangeValue(DirectCast(sender, CheckBox).Checked, 79.99D)
End Sub
Private Sub CheckBox3_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox3.CheckedChanged
ChangeValue(DirectCast(sender, CheckBox).Checked, 49.99D)
End Sub
Private Sub CheckBox4_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox4.CheckedChanged
ChangeValue(DirectCast(sender, CheckBox).Checked, 29.99D)
End Sub
Private Sub CheckBox5_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox5.CheckedChanged
ChangeValue(DirectCast(sender, CheckBox).Checked, 29.99D)
End Sub