do you think i need to use module and refernces to make any
kind of calculation? Meaning, save the calculation and
return the result when "=" is pushed
exple: if i wanna do 25 - 15 = 5

when I hit the "=" sign, it needs to retrieve the result from
where it would have been saved.

is that the right thinking?

Eureka! got it !
Dim factorielle As Double
Dim n As Integer
Dim i As Long

factorielle = 1
n = TextBox1
       For i = 1 To n
            factorielle = factorielle * i
       Next
TextBox1 = factorielle