Can I edit the MSys* tables directly?

We have a defunct replica (a design master) that was removed.  The 
Replication Manager removed the replica from the replica set; but dit not 
remove the schedule item that involved that replica.

In order to resolve the problem, I'm looking at removing a row from 
MSysSchedule for the schedule in question.  I have identified the proper
row 
in MSysSchedule, but Access will not allow me to change or delete the row.

Are these rows accessible through a VB program using DAO?  I've written 
other code to re****t on various system condition using the MSys* tables;
but 
never had to update or delete data in the MSys* tables.

Any known problems with this approach?

Thanks in advance

Don