Excel's Formula - sisman

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Part VI: Developing Custom Worksheet Functions
Consider the following Function procedure. This function accepts a range argument and
returns the number of formula cells in the range:
Function FORMULACOUNT(rng)
cnt = 0
For Each cell In rng
If cell.HasFormula Then cnt = cnt + 1
Next cell
FORMULACOUNT = cnt
End Function
In many cases, the preceding function works just fine. But what if the user enters a formula like
this one?
=FORMULACOUNT(A:C)
The three-column argument consists of 3,145,728 cells. With an argument that consists of one or
more entire columns, the function does not work well because it loops through every cell in the
range, even those that are well beyond the area of the sheet that’s actually used. The following
function is rewritten to make it more efficient:
Function FORMULACOUNT(rng)
cnt = 0
Set WorkRange = Intersect(rng, rng.Parent.UsedRange)
If WorkRange Is Nothing Then
FORMULACOUNT = 0
Exit Function
End If
For Each cell In WorkRange
If cell.HasFormula Then cnt = cnt + 1
Next cell
FORMULACOUNT = cnt
End Function
This function creates a Range object variable named WorkRange that consists of the intersection
of the range passed as an argument and the used range of the worksheet. In other words,
WorkRange consists of a subset of the range argument that only includes cells in the used range
of the worksheet. Note the If-Then construct that checks if the WorkRange is Nothing. That
will be the case if the argument for the function is outside of the used range. In such a case, the
function returns 0, and execution ends.