Expectation value of P for an infinite-square well

I just have a simple question to get me started. If I am given an initial value wavefunction ψ(x,0) and I am asked to find <P> at t = 0 can I use this:

<P> = -ih∫ψ*(x,0)$\frac{∂}{∂x}$ψ(x,0)dx

or do I need to find ψ(x,t) before I find <P>?
 No you are right (h bar)