Select the entire range A1:D15 or whatever your last cell is...

Go to Format|Condtional formatting.

Select Formula Is from 1st drop down cell.

Then enter formula: =SUMIF($A$1:$A$15,$A7,$D$1:$D$15)>10

adjust the $15 to whatever last row in your selection is...

Click Format and choose from the Pattern tab.

This highlights the rows that have a name that has accumulated more than 10 hours.