Grouping same timesheet Items on an invoice

Greetings,
We are a professional services company. I have employees working multiple days on a project. When I go to invoice via the Generate Time and Expense Invoices, I end up with many lines for each employee of the days worked on a project. I would like to combine/group each person’s hours into one line item per employee. I tried selecting the “Options” drop down and selecting the “Group by Item Type”. I thought this would work but it does not. Any suggestions would be much appreciated. Thank you.