VISUAL BASIC & CNC

Hi group,
My projects includes a controller, sensor switches, valve and
steppers. I am wondering how to write program in visual basic
(using .DLL to controll paralel port in c language) to move the
stepper without loosing step. I heard that pulse are not sent
properly in a windows enviroment and that is why most CNC programs
are writen in DOS or linux to prevent this but I need to run my
applications in a windows enviroment so my question is how can the
pulse or signal can be send properly or rechecked to the parallel
port so stepper motors can run smoothly without loosing steps?

luis..