Depends on your design. If you find records only for a given year, a simple summary field will compute the year to date total and yes, you will need to define that field and add it to your layout if you have not already defined such a field.
Stupid question does this require a script? Thats the part i cant figuire out is how to get it to give me that number.
It requires that you perform a find. That can be done either manually or with a script.
To find all records for the year 2011, you can enter find mode and enter 2011 into the date field and then perform the find. If this report is for a specific employee, you'd also enter an employee number or name in the appropriate field before performing the find.
If you are unfamiliar with summary fields, you can look that up in FileMaker Help.