I need an Excell formula that will add x$'s every 30 days

[Mark_N_Jen]

For auction site accounting - I need a formula that will add recurring fees
to a particular field every 30 days based on a date in another field.

 

[JE McGimpsey]

One way:

A1: <base>
A2: <fee>
A3: <date>

A5: =A1 + INT((TODAY()-A3)/30) * A2