(...)
Dim ex1 As Double
Dim ex2 As Double
Dim ex3 As Double
Dim ex4 As Double
Dim Sum As Double
Sum = txtResult.Text
ex1 = txtex1.Text
ex2 = txtex2.Text
ex3 = txtex3.Text
ex4 = txtex4.Text
Sum = ex1 + ex2 + ex3 + ex4
txtResult.Text = (Sum)
(...)

For some reason this one dont work..what am i doing wrong?