You need to be much clearer on what you want to achieve, else we will be guessing all day.
Do you want to create a variable?
Do you want to get info from another table based on your reports dataitem?
Can the data you want be retrieved using the primary key? IE (using GET function)
Can your data not be retrieved using the primary key? IE then using FIND, FINDSET
Do you have a copy of the Application Designers Guide? It can be found on your product CD (w1w1adg.pdf)
Or download a copy here: www.microsoft.com/.../details.aspx
It has a whole section on reports.