How to use a macro to apply damage to selected NPC

I would like to set up a simple macro to apply damage to a selected NPC.   I'm looking to select the NPC token, have it use a token action to have window come up to enter damage and apply.   Yes, I know all you have to do is click the hp part of the token bar but I'm trying to keep the experience to the character macro bar.   Any help would be appreciated. 

You will need to install tokenmod.  Also theres a very cool hidden gem out there that utilizes group check+ a scriplet called Apply Damage that does this pretty well to for niche cases involving saves.  There is a newer apply damage floating out there that also applies statusmarkers to it and accounts for advantage/disadvantage.  

This Token Mod macro should do what you are looking for. You may need to change the bar definition depending on what you are using for HP. !token-mod --set bar1_value|?{Enter damage amount. Use positive or negative to modify values|-0}

Thank you Eddie and Keith for the reply's.  I haven't installed Token Mod yet.. that is on my list for the weekend.