We have had this problem too, and the way I solve it is having a math workbook within arms reach. When I pull out our RightStart materials for the day, an additional workbook is with them.

I have three children and when the younger ones need attention, it is often needed immediately and for several minutes. If the baby needs a diaper or my Kindergartner needs help with an assignment, etc. I can stop the RightStart lesson with my oldest, hand him the workbook and say "open to the bookmarked page and work until I get back" (usually 5-10 min). That takes care of math for the day, reinforces concepts we are learning in RightStart Level B and it is fun for him.