Dear Rudy
if we define the term function as "function module" may be check: http://scn.sap.com/docs/DOC-42178; be aware of the fact that:
1.) the result you will obtain by using the standard functionalities as mentioned by Kamal are depending on your access rights
2.) that the functionality is restricted in the start screen of CG02 etc. to one spec only; if you have a "hit list" you can use this list as the starting point to get the "where used" list. It is EHS standard; there is only one "but". if you really work with a list you have no indication which spec of your first hit list is part of what spec of the new hit list; therefore this functionality (in most cases) does not really fit the cusomer demand
3. be aware of the fact that if you use a "hit list" as a starting point the topic will need a lot of time (depending on your criterias; amount of data in your database) and in many cases you will get a "out of time" dump by ABAP
4.) the standard functionality works per value assignemnt type/property; there are many value assignment types of type B or C (spec listing; composition) and therefore you will be only successful if you reduce your query to on value assignment type (in most cases)
5.) with higher SAP release you will get enhanced functionality; If i remeber correct with EnhPack 7 the "where used list" will be extended (not sure if you need to activate something)
Check e.g.:
http://www.se80.co.uk/sapfms/c/c1f2/c1f2_substances_used.htm
as well. Similar are:
http://www.se80.co.uk/sapfms/c/c1f2/c1f2_substances_used_by_mat.htm
http://www.se80.co.uk/sapfms/c/c1f2/c1f2_substance_get_comp_tree.htm
I assume that these function modules wil be caleld internyll by the BAPIs mentioned by Kamal (depeneding on the demand) but you can use them by your own as well.
C.B.
PS: regarding other SAP EHS topics related to your topic ths link might be helpful in the future as well:
http://help.sap.com/saphelp_erp60_sp/helpdata/en/e8/ebc0419e1a6224e10000000a1550b0/content.htm