Visual basic arithmetic code?

amh_soft's answer is right on, but I thought I'd add that you should make sure that the textboxes have valid input.

ex, just do an isNumeric check first

if isNumeric(textbox1.text) and isNumeric(textbox1.text) then

textbox3 = textbox1.text - textbox2.text

else

'raise error

end if

edit: I forgot to mention about the val() function, it usually works, but there's reasons not to use it.

easy enough:

TextBox3.Text = Val(TextBox1.Text) + Val(TextBox2.Text)

for both T1 and T2, you create an afterupdate event

in that event you put:

t3.value = t1.value - t2.value