wrong number of function arguments

Hello,

I keep getting the same error for my analytical function

"Wrong number of function arguments
Number of arguments expected: 3"

But as far as I can tell, I have defined 3 arguments in my function.. so I don't understand the error!

expression: a_c*pore_V(x,y,z)
Arguments: x, y, z

(a_c = a variable and pore_V(x,y,z) = random fxn)

Does anyone know whats happening?

Thank you!

Kelley