Adding client group to invoices export report

[RusselBraum]

Hello people.

I need help customizing the Report --> Exports  --> Invoices

I need to modify the above template to include the client group field. In other words, I need to generate this report so that the result only includes results from a specified client group.

I have tried modifying it myself using other reports as a guideline, but I am simply not getting it right and I don't have the knowledge to understand what I'm doing wrong.  I suspect it's probably a simple solution, just not sure where to turn for this.

Thanks in advance

Russel