Calculate daily interest rate

Some years ago I came across a formulae to calculate Daily Interest on a Building Society Savings account in the UK.
I have used this since but find my calculations never work out the same as my BS, although to my advantage!
It is =B3*B4/360*DAYS360(B5,B6,TRUE)
Where:
B3=Capital
B4=Interest Rate
B5=Starting Date
B6=Finishing Date
For some reason the formulae uses 360/year and not 365/year.
Using both still gives wrong answer.
If anyone has an answer or a better formulae I would appreciate it.
Many thanks.
I use Excel 2000