Luis,
Frankly I don't use toolbars for two primary reasons 1) this whole don't get focus subject and 2) they typically require too much mouse movement away from the form to click them. I prefer to use my own container class of buttons that's dropped onto the form itself.
In your case _screen.ActiveForm.ActiveControl.BaseClass will be "Grid". Your toolbar button subclass can test for this case and handle it appropriately by using the ActiveColumn of the grid to get the control to "self" SetFocus() to.
>Your solution doesn't work when the textbox is in a grid. Do you know how to solve this case?