TextBox & Variable Help! Can you please help?

I've researched and I just can't find what I need! I'm making a DJ Booth system, that plays the audio put into a textbox!

I need help with, scripting something that can sense what is put in a text box, and also only allow numbers in the textbox, and when they press enter, change the value of a variable (Say lets call it "djSoundID")! I've researched on YouTube, Roblox forums, this website and I can't find anything!

Sorry if I sound noob, but I'm new to scripting.

~Amp