What you suggest below will create a circular reference (i.e. you are asking
Excel to use the result of a formula as one of its arguments...the formula in
C10 cannot be computed because the vaue of C10 is required to do so, creating
an infinite loop). If this is really what you want to do, you can set the
maximum number of iterations to 1 under the Options tab...

"Barbara Harris" wrote:

from my prior post, i really do not believe I explained the problem
correctly.
Here goes again: note the function Average. Now compute Average( C1:C10).
In chronological order, C10 is the latest value. Now solve for C10 to make
C10=Average(C1:C10).

How can Excel resovle the equation?

Thanks so Much