How to make a command ignore a specific part of a label?

Let's say the following script is:
Let's say this script embeds a specific text when you type something in an input and press enter. The problem is, this script takes the whole sentence, like: when the script sees Label1 saying "creeper" it should say "aw maaan" the problem is, in Label1 there's a text in it that i essentially need, called "Guest1: " the problem here is if Label1 says "Guest1: creeper" it does not work because Guest1 exists in the label, i need this script to ignore the existance of "Guest1" so it'd be able to say "aw maaan" even if there's guest1 in the text.
Thanks.