Hi Junko,
The user-exits work perfectly well for filtering.
For Partners, use EXIT_SAPLSLL_LEG_PARR3_001 (customers) and EXIT_SAPLSLL_LEG_PARR3_003 (vendors), and simply remove any unwanted entries from tables CT_KNA1, etc., according to your requirements. For customers, table CT_KNB1 holds the Company Code assignments, so those will probably be your criteria.
For Products, use EXIT_SAPLSLL_LEG_PRR3_002. There you can un-set the TRANSFER flag in table ET_MAT_TRANSFER for any entries not to be transferred.
Hope that helps.
Regards,
Dave