Forms :: Textbox Refresh - Getting Default Value To Reappear When Change Criteria

I am using a DLookup to default a value in my TextBox. This text box has an event attached to it that updates a table when a different value is entered.

I am having difficulty in getting the default value to reappear when I change my criteria.

For instance Manufacturer is Ford

Colour is default Black

I Change the colour to red

now I change Manufacturer to Audi

I need Default colour to go back to Black

The Lookup Table says Black its just that the default value only seems to run once, first time in and never again unless i exit the database and reopen it.

I have tried adding

Form.Repaint
form.Refresh
Form.Requery
to my afterupdate query