Create Child Records

Hi,

I want to create a custom workflow activity that creates Sub Entity records based on a parameterfield specified on the parent entity.
For example, lets say parameterfield is set to '3', c.w.a should create three child records.

In workflow scenario I would add Logic as follows :

If parementfield = 3
Create 3 contacts

The c.w.a will be triggered on change of a field on the parent entity.

I am new to Development, examples and references appreciated.

Thanks,