I hired someone to create a hole in the concrete block wall for a window.
However instead of using a saw he used a sledge hammer and created a larger
hole then necessary with a very uneven edge.

Now I need to patch the concrete block with concrete cement to the desired
rough-in opening for the window. I am using two pieces of wood on each side
to help me fill in the cement along a nice even edge. However along the top
edge, I need to fill in the block wall holes with solid concrete but it's
upside down so how can I do it? I imagine anything I put up will fall down
right the way. Any tricks?

Thanks,

MC