Using Radio Buttons to start/end macro

On the attached example i have a macro behind the button 'Add Current Prices'.

What i would like to do is by using the two radio buttons (On/Off), run the macro every 'x' seconds (variable on the value of cell H8) when the 'On' button is selected and stop the macro from running every 'x' seconds when the 'Off' button is selected.

Any help much appreciated.

Adam.