ALV in Back ground..

Dear All,

I need change the layout of a ALV (from 33 fields to 22 fields in the output) with the number of characters in the header (255 Characters) and the number of Characters in the each column under header in the layout (169 Characters). Layout is changed & the output is OK when the report is run normally; but when the report is run in background, last field (22nd) is completely missing and even three characters in 21st field are missing.

Kindly let me know if <b>whats the problem in executing the ALV report in background??, why is this happening?? and what is to be done????</b>

Thanks a lot.