I think the 5th Edition OGL Companion API Script (which is available through the one click API install), has this ability. It lists "!ammotracking" as one of the script's functions. I haven't had the chance to try it out myself yet, but here's the section of the Wiki Page that has it: <a href="https://wiki.roll20.net/5th_Edition_OGL_by_Roll20#Utilizing_the_5th_Edition_OGL_Companion_API_Script" rel="nofollow">https://wiki.roll20.net/5th_Edition_OGL_by_Roll20#Utilizing_the_5th_Edition_OGL_Companion_API_Script</a> [Edit]: I tried it out and it works very well! You will want to carefully read the ammo tracking section of the wiki page since there are a few settings you need to change on the sheet to have it work. This API also does automatic spell slot tracking and a few other nice things, but you can turn off individual functions if you only want to use some and not all of them.