non-standard Hierarchy

I have a custom table having funds Group ,Funds & funds Center in R/3.

Funds Grp is the collection of some funds & every fund contains couple of Fund Centers below it .

In BW , we need a Hierarchy like :

Funds Group 1

Fund 1

Fund Center 1

Fund Center 2

Fund 2

Fund Center 3

Fund Center 4

Funds Group 2

Fund 3

Fund Center 5

Fund Center 6

Fund Center 7

………

Can you suggest me : How can I create a datasource on this & pull it in BW as hierarchy ????

Since this is not a standard hierarchy, I don’t have any standard Extractors available.

I don’t want to build it in BW manually since we have lots of Funds & fund centers & also they change very often –so cant be maintained .

Thanks,

Shalini