Finding which control triggers the Lost focus

I have a situation wherein i have a text box, that has abc()[a validation
method that leaves the focus on the same control if not validated] being
executed whenever the lost focus event is triggered. However, there is an
exceptional case where, if a button click causes the lost focus, I do not
want abc() to be called. Is there a method by which one can find out which
control is triggering the lost focus event?

I have a keyboard shortcut for the click handle, and the lost focus handle
does not get invoked if I use the shortcut. However, when I try the mouse to
click on the button, the lost focus is gettin triggered.

Any thoughts?

Cheers!
Nicj