Number sequence customization

I have a Number sequence to generate for instance like 5600023000. the first digit 5 is constant.digit 600023 represents id and last three digit are digits that need to be incremented till n-1(like 999) if the last three digit reaches 999,the id has to be increased by 1 like 600024 and again the last three digit will start from 000…so,finally new number sequence become ,5600023999,5600024000,5600024001 and so on…plz…help how to customize the code for this number sequence.

Hi Kalpana, Did you find any solution for this customization if any please guide me.