I am a relative noob when it comes to VBA etc so please bear with me.

We have a worksheet with four columns (and an embedded formula) reaching to Row 100 then the calculations stop. I have tried copying and pasting (doh) from the first 100 rows into the next 100 but that clearly doesnt work. How can I unearth the program/macro going on behind the scenes just to extend the range that it calculates from 100 to 500 for example ?