Variables can be applied to make this easier. Create a variable with a default value of zero (remember not to put spaces in your variable name). Then make an event like this:
- when
- - and
- - - or
- - - - key pressed
- - - - - Spacebar
- - - - key pressed
- - - - - left ctrl
- - - =
- - - - variable name
- - - - 0
- - modify variable
- - - variable name
- - - 1
Then simply make when - true events to change the IFFs and abort the mission, and then chain them to it with the appropriate chain delays. You'll also need to set up an event to modify the variable up to 1 when your cover has been blown and it's OK to fire again.
I think that should sort you out, though I'm doing this off the top of my head rather than setting it up and testing it in FRED.