Solution

Dicey Operations Elspeth

First name
Elspeth
School
Banstead prep school
Age
11

The closest I could get to 1000 was 999. 
My strategy is to sart whith the hundreds so that you can be sure that you will get around 1000 after I have put the the hundreds in place I do the tens and so on.

It is harder if your numbers are to big or small.🦆