Transfer ITAB contents to PDF format

Hi,

I want to transfer ITAB contents to PDF.format. For this iam following above steps:

(Note: my output in Z-report1 is in classical format and year wise but in output it contain all 12 moths data so i want to generate new PDF file for each month separately if i run this report in background then it will generate only one spool request for all 12 months)

1) Z- report through which iam transferring ITAB comtents to memory ID.

2) then through SUBMIT iam calling new Z-report1.

3) then iam importing ITAB content to Z-report1.

4) Now to get the Spool no i want to execute Z-report1 in background (automatically it should run in background because iam calling Z-report1 in Z-report).

SO is there any function module so that i can pass report name (Z-report1) and it will run in background

Please help.

Thanks .

Regards.

Hemant.