An integral equation theory and Monte Carlo simulations are applied to study a model macroion solution confined between two parallel plates immersed in a 1:1 electrolyte and the macroions' counterions. We analyze the cases in which plates are: (a) uncharged; (b) when they are like-charged to the macroions; (c) when they are oppositely charged to the macroions. For all cases a long range oscillatory behavior of the induced charge density between the plates is found (implying an overcompensation/undercompensation of the plates' charge density) and a correlation between the confined and outside fluids. The behavior of the force is discussed in terms of the macroion and ion structure inside and outside the plates. A good agreement is found between theoretical and simulation results.