Hi, i've got a spreadsheet with a function i would like to duplicate:

There are 2 cells, one with the Yield of a security (in this case a bond) and another cell with the price of the security (the same bond). Lets say A1 holds the price and cell A2 holds the yield. Now Excel functions Price() and Yield() use more or less the same arguments and let you calculate the Price of a bond, based on a certain yield OR let you calculate the yield of a bond, based on a certain price. So it's a bit like the chicken and the egg...you need a price to calculate yield or you need a yield to calculate a price.
In this spreadsheet i'm having they allow you to type in the Price of a security in cell A1, which will give you a yield in cell a2. The nice thing however is the following: if you type a yield in cell a2 it will give you the price in cell a1. So based upon your input Excel looks at the cell where you have input the value and puts a function in the other cell....it calculates the result and puts the original function back into the cell where you have just typed a value, allowing you to do further calculations with that function....So even when you type a value in a cell, somehow excel still knows what functions should behind it once it has done it's calculations......Maybe i'm not explaining this very well but if someone has any idea how you can do this i would love to hear from you ! Thanks in advance!!!!