Don't know about the fastest, most efficient, but

Const dEPSILON As Double = 1E-10 'set appropriately
If Abs(Cells(21, 1).Value - 1) < dEPSILON Then ...


will work. Using Range references (Cells(21,1)) instead of the evaluate
method ([A21]) will likely speed up your code more than which method of
testing you use.



In article ,
"Peter T" <peter_t@discussions wrote:

The various methods I've tried to eliminate "false" results slow the process
at least to some extent, inevitably I suppose. My purpose and the point of
this post is to do exactly what you suggest:

"design your programs to be tolerant of the approximations inherent in
floating point numbers"

But in the fastest most efficient way possible.