IN BEHALF OF or ON BEHALF OF?

What is the difference between in behalf of and on behalf of? 

In behalf of means "for the benefit of" or "in the interest of."

For example:  The First Lady hosted a charity dinner in behalf of the street children of Metro Manila.

On behalf of means "in place of" or "as the representative of."

For example:  On behalf of the President, the First Lady thanked the people for their loyalty and support.