Circular calculated control?

Hi all,I have the following fields on my form and underlying table: [Net Initial Yield], [Rent Per Annum] and [Price]. For some record entries all of these fields may be filled in, but for others only 2 fields may be filled in (which 2 these are could change each time). Is there some way of making it so that if one of the 3 fields is empty, a calculated control works out the figure? The sums for working out each are as follows:Net Initial Yield = (([Rent Per Annum]/[Price])*100)Rent Per Annum = (([Net Initial Yield]/100)*[Price])Price = ([Net Initial Yield]/100)/[Rent Per Annum])I’m not sure how to write an expression or code to say, if [Net Initial Yield] is left empty, calculate it and fill it in as follows: (([Rent Per Annum]/[Price])*100)And if [Rent Per Annum] is left empty, calculate it and fill it in as follows: (([Net Initial Yield]/100)*[Price])And if [Price] is left empty, calculate it and fill it in as follows: ([Net Initial Yield]/100)/[Rent Per Annum])Obviously the field needs to be able to contain a value if one is added, OR work out the calculation if not. I hope that makes sense!! If anyone is able to help, it would be very much appreciated!!!

Circular calculated control?