TIMESHEET - time calculation for multiple jobs type

Hi

Have a look at the attached timesheet.

I'VE ATTACHED WRONG FILE, SORRY GUYS. CORRECT FILE IN POST #4

I want to be able to calculate times I have spent doing different jobs types.
There are 5 job types MAINTENANCE, REPAIR, INSTALL, EXTRA WORK and OFFICE WORK and i would like automatically summarise time spent
on each TYPE of job at the bottom in cells D20, D21, D22, D23, D24
So I need to find a way for Excel to add all hours I have spent doing MAINTENANCE for example.

I think that the way to do that is to use a formula that would look for word MAINTENANCE in column J and then add all the hours from column I for the rows with word MAINTENANCE. After adding all those hours the summary would be displayed in cell D20. And then to do same for other types of jobs.

I just simply haven't got a clue how to do that.

I will be grateful for any help!