Finding an API service for ( Group Shouting while using in-game GUI ) ?

Okay first of, i discovered that you can actually shout group messages within the game by scripting a simple gui in a textlabel, Rather than going to the web-page finding where your group is and shouting a message. I find this very useful in different ways. so i tried researching in Roblox Wiki, Robloxdev. i can't find any API of it or at least didn't find it my self. if anyone who can link it to me or at least show me how i would be very appreciate it.