how can i do the deltas from the R/3 Custom Table

hai

I have data in EKKO , EKPO and sone other R/3 Tables. How can i extract this data into BW.

Is it good to create the custom R/3 table in R/3 source system and populate the required fields into that R/3 table.If it is ok then how can we do the deltas.

We need to load the deltas monthly.

Pls tell me . i ll assing the points

kumar