WPF Control

Hi all,

I want to create a Spinner Control without the help of third party Assembly,not yet Wpf ToolKit also.

I have 3 textbox A,B,C in and two button X,Y.
the text box only accept numbers.

I want the value of the Selected TextBox A will be updated when i will click Button X(add 1 with A.text) or Y(sub 1 from A.text).

and the same for the other 2 textbox also.
I have tried something like 
 
private void X_Click(object sender,RoutedEventArg  e)
{
        if(A.IsFocused)
        {
                //////
        }

}
but when i am clicking on the Button the focus is changed and it is not working..
Can some one help me out.

Thanking you,
Arijit Naskar