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Chapter 20: Creating Worksheet Functions — and Living to Tell about It
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argument. The LBound and UBound functions determine the beginning and
ending elements of the array. The beginning element is normally 0 unless you
either declare it as something else or use an Option Base 1 statement at the
beginning of your module.
ParamArray can apply to only the last argument in the procedure. It is always
a Variant data type, and it is always an optional argument (although you don’t
use the Optional keyword). Figure 20-2 shows this function in use. Examine the
figure to see how the results differ from those produced by the Excel
CONCATENATE function, which doesn’t insert a space between the concatenated
items.
Figure 20-2:
Using the
Concat
function in
worksheet
formulas.
Functions That Return an Array
Array formulas are one of Excel’s most powerful features. If you’re familiar
with array formulas, you’ll be happy to know that you can create VBA functions
that return an array.
Returning an array of month names
I’ll start out with a simple example. The MonthNames function returns a
12-element array of — you guessed it — month names.
Function MonthNames()
MonthNames = Array(“January”, “February”, “March”, _
“April”, “May”, “June”, “July”, “August”, _
“September”, “October”, “November”, “December”)
End Function
To use the MonthNames function in a worksheet, you must enter it
as a 12-cell array formula. For example, select range A1:L1 and enter
=MonthNames(). Then use Ctrl+Shift+Enter to enter the array formula in all
12 selected cells. Figure 20-3 shows the result.