What have you tried?
Are you a total beginner? Or do you have some experience?
Which script language are you planning to use?
Which version of InDesign?
Iam using Indesign CS5.5.
I know VB Script little bit.
The basic technique I'd use would be to add rows after the row of interest and then move the last paragraph to the corresponding cell on the next row (that you just added) until there's only one paragraph left in the cell.