Vista - WPF custom user control

I am in the process of developing a custom user control derived from Control.
It has textbox and a button. I managed to catch the button click. To dothis I
have implemented dependecy properties and routed commands.

Eg: in my generic.xaml
<RepeatButton Command="{x:Static
local:myInputBox.KeyPressCommand}">Up</RepeatButton>

This is work fine. But I cant catch the textbox LostKeyboardFocus evnt. When
I try to implement this like the way I did for the button, then getting an
error as bellow.

"not a valid event handler method name. Only instance methods on the
generated or code-behind class are valid."

Please help me to over come this problem. Apreciate your early response.

Thanks.