Using picking with Directinput

i''m working on something that requires opengl picking, i spent a day or less reading and i''m now capable of doing it(the opengl part), but i need the mouse coordinates relative to the window coordinates so that i can perform picking, i tried to use directinput, but 1)it gives me the amount of movement since the last call, (i managed to convert this to absolute coordinates, but this annoyed me) 2)i feel it''s not accurate, mayb coz of that windows mouse acceleration thing, i don''t know. do i switch to GetCursorPos() and save some effort getting directinput to do it, does GetCursorPos() have any drawback/disadvantages?? thanks for help xee..