Custom Control's Properties in Design Time

I've got a custom control that I'm working on which has a
property that is somewhat analogous to the DockPadding
property in other controls (ALL, left, right, top, bottom).

I've put together a type converter that returns the
correct information with one exception: when I change the
all property, I'd like the property grid to display the
value for the rest, as does the DockPadding property.

When I select the individual values, they change the
display, but I much rather have them change automatically
upon modification of the all property.

Thanks,
-Dan