Hi Tig just to thank you for your advise.

I found if I had blocked the EXTG earlier and then blocked the proposed later it wouldn't work. However each time I modify my proposed I simply just explode the EXTG and block each one individually with out moving them in the screen. this seems to work every time then.

Hi all trying to cut and fill this split level into a site any one help as to why its not working, novice sketchup here the tool looks amazing once I get it going it will be invaluable for calcs!

trialing.skp