Hierarchial / Structural Search Help Exiit for 'Material Group'.

Hi Experts,

I need to create a Hierarchial / Structural Search Help Exit for 'Material Group'. (The same standard thing is implemented for Tcode PA20 in 'POSITION' Field). With prelim analysis I found the function module 'RH_OBJID_REQ'. But I dont know how to and where to use this.

Can any expert please tell me the step by step process of creating a Hierarchial / Structural Search Help Exit for 'Material Group'.

Thanks in advance.

SD.