How to can "mouse wheel" and "keyboard type" at the same time in Slider?

Hi all,
I have a Slider, I can wheel the mouse or type to textbox to change the value of the slider. But Slider only focuses on “mouse wheel” or “textbox”, if I’m editing textbox, I cann’t wheel the mouse and vice versa. How to do the 2 actions at the same time? Thank all of you so much for your help.