Odd - and probably basic error

Hello

I am facing to this odd problem.
It is probably a simple issue, but I can't find the solution

I am calling a sub, in order to
- load some values from a form in an array
- I am calling this sub

this sub is called with

calculate_X A__Curve

while I am declaring this sub with

Private Sub calculate_X(pt As CURVE)

x_1(1) = pt.01
x_2(1) = pt.02
x_3(1) = pt.03
x_4(1) = pt.04
y(1) = pt.i_11
y(2) = pt.i_12
y(3) = pt.i_13
y(4) = pt.i_14

End Sub

I get following error

Sub or Function not defined

Please, can anybody help me ?

thanks