GW Function Import: pass parameter table (e.g. multiple parameters of same type)

Hello GW experts,

we have defined a Function Import "CreatePOWithReference" with a parameter "Reference" which contains a string with information about a reference document which shall be used to create a new Purchase Order (PO):

Now I would like to pass not only a single reference but multiple reference all of the same type "Reference".

I tried calling the function import with two references like this:

/sap/opu/odata/sap/ZMP_ODATA_PO_SRV/CreatePOWithReference?Reference='123'&Reference='456'

But in method "/IWBEP/IF_MGW_APPL_SRV_RUNTIME~EXECUTE_ACTION" my parameter table "IT_PARAMETER" only contains 1 single record:

How can I achieve that the table "IT_PARAMETER" contains two records (Reference='123' and Reference='456')?

Thanks and best regards,

Oliver

PS: As there can be any number of references, it is not an option to create several parameters "Reference1", "Reference2", "Reference3" and so on... .