Is it possible to track an individuals contribution to Tasks when they only work a few hours a week?

I'm trying to plan and budget for the completion of several tasks. I have some workers who work a few hours a day, but not every day. So whilst I can allow, say, 20 working days to complete a particular Task, does Mind Manager allow me to allocate a few hours per day for each individual to be working on these Tasks? I'm new to Mind Manager and it seems I can allocate 20 working days to complete a Task in, however the software assumes I'll be paying someone for every full day, when in reality I'll only be paying for the hours actually worked. I want to be able to show that some of my workers will only spend 2 hours per day, for 3 days per week on some of these Tasks (and that's why it will take 20 days to complete).

I hope I've explained that adequately.

Mike.