Hi Kiran,
Use static variables [Tables], or GDC or Component Usage.
Ucan use any logic for getting data from diffrent components.
and all the data put in one internal table create one button[Download ] in to Viewset and In event : EH_ONDOWNLOAD write the logic to fech the data and make the data into EXcel format [some standard clases are there for the logic,search it 
], go to View set.Htm File create File path setting code,
please find attached for refference, that is for upload same for down load also.
thanks,
venkat.