column a = staff ref
column b = surname
column c = first name
column d = PT worklog start date
column e = PT worklog end date
column f = pay grade
column g = cost centre
column h = duration
column i = hourly rate

That is the setup of the above example, the duration field shows as
01:30 which i have formatted to [H]:mm. however when i drop the formula
in to column j row j2 it doesn't calculate the total hours for some
staff and shows as zero.