C# listbox help

Question

Hi

I have many buttons and a listBox.
In every button I have a code like this: listBox1.Items.Add ("different for every button");
but if I press 2 different buttons I use 2 lines
is it possible to press 2 buttons and write the text in the same line?

like one button says: Hi
and another one say: you
and when I press both it wont say it like this:
Hi
you

but like this: Hi you
in the same line. 
hope you understand what I mean.