Get planned order number(PLNUM) or requirement number(RSNUM) of a BOM item

Hi everyone!

I have a material...viewing it at MD16..i can now see the stock/requirements list displayed in a tree. Now i have below hierarchy:

material 1       ----> has                planned order number
       material 2  ------> has           requirement number
             material 3  ------> has       planned order/requirement number
             material 4  ------>  has       planned order/requirement number
material 5 ------> has       planned order
material 6 ------> has       planned order

using the planned order number of material 1 in the BOM, i was able to get the requirement number of material 2, what i want to know is how to get the requirement number of the next level under material 2...that is, the planned order/requirement number of material 3, material 4 ....

thanks!