If you decide to risk not splitting, you need to get the Windows user login name and find that in a table of users. Research ms access Windows user login or something similar. There are several options, one is the built in Environ username property. Also need a table of forms vs users and the filters for that form/user combo. Recommend not using literal sql text as I've seen cases that suggest it can't be resolved in vba. You can concatenate the filter values from this table into a sql string in code and apply that on the necessary form event. AFAIK, each user is opening a copy of this form in such a shared environment and their application of a filter won't affect anyone else. However, whatever the form is bound to will be affected by concurrent users, which means that conflicts can occur in terms of record locking depending on that setting.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.