Stop calculating after a certain date

Hi,
I am trying to put together a plant register that calculates the costs from on hire and off hire dates. I am using IF function, which does calculate the cost between the two dates and stops accumulating in the to date total cost, however I also have a weekly cost which I want to return a result of 0 if there is an off hire result and this exceeds Todays date so it does not accumulate in the weekly total. I cant delete this line as then the to date total cost will be in correct.

As I send out the plant register every Friday I want this cost included up to the friday of the week off hired. Once this has been exceeded then I want this to return a 0 result to it does not contribute to the weekly cost.

Therefor I am looking for this formulae;-
If start date is more than todays date then return 0. If off hire date is entered then include cost until the Friday of the off hire week. Once Friday of that week has passed then put 0 to stop counting.

I have a formula which automatically calculates the next Friday, but this changes as its based on todays date, where as I want it fixed from the off hire date =TODAY()-CHOOSE(WEEKDAY(TODAY()),2,3,4,5,6,7,1)

Any help would be great :-)

Thanks