subordinate org units 3 level deep

Hi,

We need to fetch subordinate org units up to 3 level deep
for a manager to be displayed in mss team calendar.

   O (Manager's org unit)

   |

   -----O1 (level 1)

          |

          -----------O2 (level 2)

                       |

                       ----------O3 (level 3)

I have used standard FM RH_STRUC_GET but no help. Can you please guide.

Thanks

Arindam