Grid Editing Control doesn't always update the Binding Source

   I have a custom editing control (Nullable Date Picker) for use in a grid, and no matter what I try, I cannot get it to work properly. I am almost there, but there is one last thing that just won't work!

If I edit (TextBox) the value in the control, and then click another cell in the grid, the value is accepted and the binding source is updated.

However, if I press the Tab key to move to the next cell, the value is discarded and replaced with the previous value. All the relevant events fire (TextBox.Validating, TextBox.Validated etc), but the value is not updated in Binding Source.

Upon further investigation, it appears that the CurrentItemChanged event of the BindingSource is only fired if I change focus with the mouse. 

I know that I'm close to getting this to work, but I just can't figure out why it would work when changing cell focus from a mouse event and not a keyboard event!

Any help would be greatly appreciated!