Update rules??

Hi,

i have a scenario where in a single value is coming from a field A1 from R/3 and i want to feed this to ODS to three infoobjects like IO1, IO2, IO3 (all are key figures)

basing on a combination fields value B1

so the logic will be like this

if B1= 100 then fill A1 value into IO1 and IO2

if B1= 200 then fill only IO1

if B1= 150 then fill IO1 and IO3,

can i do this in routine r else do i need to do it in startroutine.

thanks and regards

Sreedhar