run a shell command with textbox

I'm trying to run a command like this

Private Sub run_Click(sender As Object, e As EventArgs) Handles run.Click
shell ("ping -textbox1.text-") (where -textbox1.text- is the user defined IP from textbox)
End Sub

but I'm having a brain fart and can't figure out how to call the textbox.text...

thanks for your help in advance