Please help

[Tamecia Medley]

I have a business right and I wanted to know is their any
way like if my customers do not pay their bills on time
that Excel could calculate a interest rate for me every
thirty days if I let the computer know that they have not
paid

 

[rick]

I'm not sure exactly what you mean it sounds like there is
a number of ways you can do what I think you want to do.
An IF,AND formula may be the easiest. if there is no
payment in the amount paid column after 30 days from
billing date then add interest to total bill

=if(and(now()-A>30),(B=""),c+interest amount,"")

a= billing date cell
b= amount paid cell
c = billing amount cell
the total of this formula would be the new billing amount