I need to send a constant stream of characters through Bluetooth when a button is pressed.

[will...@gmail.com]

I have the Bluetooth configured already. What i need is when the up button is pressed it sends "F", "F", "F", "F", "F", "F", "F", "F", "F" Until it is no longer pressed then when nothing is being pressed it sends "S", "S", "S", "S", "S", "S", "S", "S", "S". I am very new to app inventor and I am making an app to control my Bluetooth robot. I appreciate any answers