[Help] Add to TextBox[Solved]

How do you add additional words into textbox.text w/o messing up the lines already in the textbox.

for example.
in the textbox there is the line "Hello world!"

when i click this button it adds the word "Bye!" after the hello world"

so final text is "Hello World!Bye"

textbox1.text = "Bye!"


try that one

lol it will erase the line "Hello World!".....