on (someone's) behalf
acting as someone's agent, acting for the benefit of someone
I was able to sign for the registered letter on my wife's behalf.
Makeup for Valentines Day
Choose a loose iridescent powder that matches your natural skin tone for a romantic glow. If you have a darker complexion, choose a golden powder. To avoid shine, dont apply the powder over wrinkles, acne, or other imperfections. Apply it only to the smoothest parts of your skin to highlight your best features.