Fomula to return diff results based on criteria?

Hello All

I am trying to figure out which formula to use in the highlighted part of attached workbook.

In Green box - hours actually worked
In Purple Box - contracted normal hours.

In the RED box - is the difference between contracted hours and hours actually worked. (extra hours worked) - I think I have this right. But need it to also reflect 0:00:00 if Green & purple both say 76:00:00. i get a multitude of ###### at the moment if these match.

In the BLUE box are the hours (OVER max 10 hrs pre approved) - so in example given, I need this to reflect 7:12:00 as 10 hours of the 17:12:00 are pre-approved and forms for the 7:12:00 must be supplied.

However - at same time if contracted hours and hours actually worked are both 76:00:00 - I need this also to reflect 0:00:00

I am struggling! Thanks for any assistance, much appreciated.

ha! yeah I am self taught and a bit old school

Thanks very much! that worked.

Would you please have any ideas for the blue cell?

Thanks again.

Thank you that has worked - however I just need to get it to read as a zero if RED sum is less than the 10:00:00 rather than blue showing as negative hours.

got it!
I was even able to figure out what "cell" and "formula" should be, all by myself :D
Thanks so much! I really appreciate all your help!