VB triganom

If Trim(txtheight.Text) = "" Then txtheight.Text = 0
rad = txtrad.Text
rad2 = rad * rad
rad3 = rad * rad * rad
high = txtheight.Text
third = 1 / 3
pi = 3.14159265
ft = 4 / 3
    If IsNumeric(rad) Then
        If IsNumeric(high) Then
            If oppyrvol.Value = True Then
                Sum = rad * high * third
                lblansvol.Caption = Sum
            ElseIf oppyrarea.Value = True Then
                MsgBox "This Command hasnt ben finished yet."
            ElseIf oppyrcirc.Value = True Then
                MsgBox "This Command is useless. it CANT be done. The radio button is just for show."
            ElseIf opspherevol.Value = True Then
                Sum = ft * pi * rad3
                lblansvol.Caption = Sum
            ElseIf opspherearea.Value = True Then
                Sum = 4 * pi * rad2
                lblansarea.Caption = Sum
            ElseIf opspherecirc.Value = True Then
                Sum = pi * rad2
                lblanscirc.Caption = Sum
            ElseIf opcylvol.Value = True Then
                Sum = pi * rad2 * high
                lblansvol = Sum
            ElseIf opcylarea.Value = True Then
                Sum = (2 * pi * rad2) + (2 * pi * high)
                lblansarea.Caption = Sum
            ElseIf opcylcirc.Value = True Then
                MsgBox "This Command is useless. it CANT be done. The radio button is just for show."
            Else: MsgBox "Please check a button."
            End If
        Else: MsgBox "The Input must be of numeric value!"
    End If
End If