Is there an easy to to programmatically force a uielement to validate in Silverlight 3?

I have a textbox where i bind a `Silverlight.Validators.RegexValidator` to, unfortunately the validator checks against another uielements content (combobox). Normally onSelectionChanged on that combobox - its selected item is set in the validator, and when the textbox content changes (key presses), it checks against this.

But i also want to run the same validation again when the combobox selection changes

can i do something like `myTextBox.Validate();` or even something like `myTextBox.KeyUp()` to force validation? 

Thanks