How can I do this with DEFINE REPORT...

[HunterEC]

Guys:

I need to code the following report but I don't know how:
I'm using 3 files:
a. Inventory
b. Sales
c. Purchases
The report should display the following:

Item 1: Inventory description + other inventory data
Group (with totals) all transactions from the sales file
Group (with totals) all transactions from the purchase file

Item 2: The same layout.

Thank you for your help.