Usually, data filtering is not done at the SAP Connector level since that would mean moving away from a single connection-single account-cost-effective connection, to a different SAP User for every other connection.:
You could use an additional WHERE clause in the VB* SELECT statements, but even that technique may pose problems sooner or later. Moreover, separating and reducing data this low in the stack almost always results in multiple overlapping QlikView documents which must be managed and maintained (how do you handle users that should be able to see everything?).
The most common QlikView technique is to load everything from the source systems, process everything through all intermediate Data Transformation steps, and let the top-level UI document decide on what a particular user can and cannot see. Section Access in combination with Data Reduction is a simple and efficient tool for this kind of data authorization.
If you have a Publisher license, the QlikView Publisher can be used to create different top-level documents for different users, each one containing no more data than the end-user is allowed to see/use.