Excel's Formula - sisman

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Part VI: Developing Custom Worksheet Functions
A more general function, one that accepts array constants as well as ranges, is shown here:
Function DRAWONE2(rng As Variant) As Variant
‘ Chooses one value at random from an array
Dim ArrayLen As Long
If TypeName(rng) = “Range” Then
DRAWONE2 = rng(Int((rng.Count) * Rnd + 1)).Value
Else
ArrayLen = UBound(rng) – LBound(rng) + 1
DRAWONE2 = rng(Int(ArrayLen * Rnd + 1))
End If
End Function
This function uses the VBA built-in TypeName function to determine whether the argument
passed is a Range. If not, it’s assumed to be an array. Following is a formula that uses the
DRAWONE2 function. This formula returns a text string that corresponds to a suit in a deck of
cards:
=DRAWONE2({“Clubs”,”Hearts”,”Diamonds”,”Spades”})
Following is a formula that has the same result, written using Excel’s built-in functions:
=CHOOSE(RANDBETWEEN(1,3),”Clubs”,”Hearts”,”Diamonds”,”Spades”)
I present two additional functions that deal with randomization later in this chapter (see the
“Advanced Function Techniques” section).
Calculating Sales Commissions
Sales managers often need to calculate the commissions earned by their sales forces. The calculations
in the function example presented here are based on a sliding scale: Employees who sell
more earn a higher commission rate (see Table 25-1). For example, a salesperson with sales
between $10,000 and $19,999 qualifies for a commission rate of 10.5 percent.
Table 25-1: Commission Rates for Monthly Sales
Monthly Sales Commission Rate
Less than $10,000 8.0%
$10,000 to $19,999 10.5%
$20,000 to $39,999 12.0%
$40,000 or more 14.0%