How to show details in Group header

[Ravala1]

I have two groups in the report:
1. Invoice Number
2. Invoice detail.
I need to put comments from details as concatenated string before details.
If I have teo details with 'comments of detail 1' and ''comments of detail 2',
my report should show:
Invoice No-123456
description:
comments of detail 1
comments of detail 2
invoice Details:
.....

How can I do it?
Please help, it's urgent.

[shakti5385]

Can you please what reporting method you are using, Data report or CR.
What are the table field please explain little more your problem, because I am not able to understand what you are saying.
Have you use any formula filed in the report if you are using the CR.

[Ravala1]

I use Crystal Report XI.
Let's say Table Invoices is linked to tables Invoice_details and Invoice_items.
Invoice_details is hours, rates, comments
I have to separate Details and items in two different group,
But before this two groups I need Comments from details.
I have to take one part of detail, comments and show it in group 1 header,
than in detail section: hours and rates

[shakti5385]

You can make the formula according the the group header and the detail section , and then you are able to use it.
Try with the formulas in the CR