A family of Microsoft relational database management systems designed for ease of use.
What's the context? Are you using an Unbound Form with controls named txtName and so on? Are you copying data from a mainform to a subform (or the subform's Table)? If so why?
Secondly, you (at least in words) seem to be mixing Forms with Tables. Forms don't store data; only tables do. Is tblClients_Subform a Form or a Table? If it's a Table, do you have an open subform bound to it?