Need to do the simplest calculation in VB, but it keeps freaking me out;

I have the following code;

Private Sub Command1_Click()

decVacuumperif = decAttpitch1 + decAttpitch2

End Sub

.. if i put 1 in Attpitch1 and 2 in Attpitch2 and execute i get 12 (!)
So, i does not calculate, it just puts the numbers after each other.

Please help me out, i'm really new to this..

Because decAttpitch1 and decAttpitch2 contain strings. Declare them as Long or do the following:

decVacuumperif = CLng(decAttpitch1) + CLng(decAttpitch2)