Hi Naga
I am not sure if I have understood your point correctly since you have mentioned you have created update rules between standard and custom infocube.
Assuming two scenarios, am giving you these options
If you want to load data from standard infocube to custom infocube
Right click on the first standard infocube and select generate export datasource which means your first infocube will be considered as a datasource. Later you could create update rules using that generated datasource to load data into the second infocube.
Below information will help you to load data to both infocubes from the same datasource
This is pretty simple. You already have the datasource in place. So just create the update rules having the existing datasource as your source from second infocube.
In both scenarios, you need to create infopackages and hope you are aware of this.
Please explain in a better way with more detailed information if the above two are not your requirement.
Regards
Karthik