The way you've described it set your main form to split form and see if
that's the option your looking for.

You could also try the following to see if this get's you anywhere:

Create a new tabbed form (i assume you don't mean tabcontrol but actually a
tabbed form). Place the form in design mode and drag your source directly
onto this form. This will create a subform. Set the subform to split form and
see if that's the result you are looking for. If so adjust the original
setting to the one just created.

hth