Disable ringer volume changes when phone locked

[chapelstboy]

Hi,

My phone's ringer volume can be changed even when it's locked if the screen is turned on (by pressing the power button once). I don't want the ringer volume to be able to be changed unless the phone is actually unlocked. Is there any way to achieve this operation?

NB: I still must be able to adjust the media volume if the screen is off.

 

[chapelstboy]

Anyone?