Interesting VBA effect ???

Hi all.

Slowly I'm picking up the basics of VBA. I've created a few macros including one with a three button user form. By accident I've discovered an odd issue/characteristic of the macro.

When I first open the User Form the Apply button (Command Button 1) can be activated with the Space Bar on my keyboard. It only does this once. The button can be used to update the effect, but I must click it after the first space bar activation.

If I don't select an object and the message box opens informing me of this the space bar will close the message box. Once the effect is applied though, I have to click the buttons.

I have not included key functionality of any kind so, although of no real concern I'm curious to know if this is a feature or some weird code issue

Thanks in advance.