I have the following problem: I would like to solve the system of nonlinear equations by Newton method in VBA but do not know where to start.

The equations:

Q=A_he*k_he*((t_zs-t_zg-t_ps+t_pg)/(ln(t_zs-t_zg)/(t_ps-t_pg))
Q=A_g*k_g*(t_zg-t_pg)/(ln(t_zg-t_w)/(t_pg-t_w))
Q=G_g*c_w*(t_zg-t_pg)
Q=A_b*k_b*(t_w-t_z)
G_g*c_w*(t_zg-t_pg)=G_g*c_w*(t_zs-t_ps)

The unknowns: Q, t_zg, t_pg, t_w, t_ps


Thanks for any help,
Adrian