Extracting formulae from regression line automatically

[ICPurvis]

I have several curves to which I have added regression lines, mostly of the form y=a*x^b, and I have to format the formula as numbers and increase the number of decimal points so that I can pick up the less significant digits. I then paste this formula into a new cell and replace the "x" with the address of the cell in which the measured value of "x" is located. I then copy this formula down to give me the calculated values of Y, which I can then use to calculate values for use on other sheets of the workbook.
Is ther an way of automating this process, preferably without having to use VB or other external programming?

 

[ICPurvis]

I have been advised that it may be possible to use Statistical Functions to solve this problem, but I can only find Linear and Exponential functions (LINEST and LOGEST). Does anyone know of a similar function to fit to a Power function (POWEREST???)?
Regards, Iain