Compare values

[Navhonda84]

Hi Guys,
This is my first post, need some help on a small formula.
What i need is to compare a specific term from a row and then add the relavent values along that term and display.

I have a list of Categories, CAT1, CAT2, CAT3 and CAT4 and I have tasks against it and allocated hours
What I want is to add the hours against each CAT and populate it in a column.
So even if i add new tasks at the bottom it shud automatically pick up the CAT and add to the final value....
Does that make sense...
I am attaching a simple file.. please help...
I think i need an IF formula, like (relates to the file attached)

=IF(h3:h17=CAT1,sum(etc....), thas were i am stuck

I will write the formula like I want the solution to be,

=IF(h3:h17=CAT1, sum(4 columns along that CAT), "")
The same for all the CAT's..

Does this make any sense...????
And I am using Office 2003.... PLease Help