How to create custom Module based on Quote and Invoice?

Hello,

i need a custom module that ist based on the Quotes Module to use most of the Features and convert it easy to an invoice.

I am using the current Quote & Invoice Module already for yearly subscribtion-fees of my clients. I need a second module to handle a fee for successful commissions. I think it makes very much sense to use a seperate Module. I know how to create one and handle relationships but how can i handle the problem with the converting the module to invoice? Is it possible to set up a second Quote Module and a second Invoice Module?

Anyone here with experience?

Will be awesome.

Thanks, Sma