Execute Case Structure with Button Press Slows Down VI

Hi -

I'm fairly new to LabView, and I am having some issues with using a button to run a timed while loop.

I am writing a VI that outputs a timed voltage pulse to an output channel on a DAQ; meanwhile, the VI reads and graphs the voltage on three input channels on the DAQ. When I use a timed loop that automatically executes when the VI runs, the program works. However, I would like to include a button so I can control the timing and number of voltage pulses sent to the output channel, instead of sending only one voltage pulse each time the VI runs. I have tried to do this using a button wired to a case structure. If the button is 'true,' the VI should send the voltage pulse. If the button is 'false,' the VI should keep the voltage at zero.

When the button is 'false,' the VI runs normally; however, when the button changes to 'true,' the VI slows down and never sends the pulse. Why does this happen? How can I fix it?

Also, how can I send the voltage pulse only when the value of the button changes?  I only want the timed loop to execute once when the button changes value.

Thanks for any help or advice!!!