Date Calculations

I want to be able to compute the difference between two dates (easy enough) but then want to beable to compute the number of months (up to half months in frequency.

Example: In this case employee was terminated.

01/1/09
08/18/09

Calculate the number of months up to half months. I would like the comutation to return the answer of 7.5 months.

I am doing this to compute payroll for a small office for budget calculations.

So the formula must also take into account the employee start date (if(year (x) < year(y-current year) then return a months worked value of 12), else compute the number of months.

AS WELL, the formula must take into the situation above whereby the employees left or was terminated and compute the months worked based on the END date.

Thanks for any help.

I did figure this out. I used a start date column, first of the year constant and end date column. However, I cannot figure how to round to the nearest half month.

IF(AND(YEAR(A2)<YEAR(B2),YEAR(C2)>YEAR(B2)),12,IF(YEAR(A2)<YEAR(B2),(C2-B2)/30,(C2-A2)/30))

A2=Start Date
B2=First of Year
C2=End Date

Any help is appreciated.