This is Not the right place to ask these questions, use Code Project.
But since I'm here.
If you are talking about 200 - 100 = 100 then
Dim Num1 as Integer = 200
Dim Num2 as Integer = 100
Dim Result as Integer
Result = Num1 - Num2
' output result to where ever you want.
TextBox1.Text = Result