Excel's Formula - sisman

Chapter 25: VBA Custom Function Examples 703
First, change the argument from a String data type to a Variant. If the argument’s data type
is String, Excel tries to convert whatever it gets (for example, number, Boolean value) to a
String and usually succeeds. Next, the Excel ISNONTEXT function is used to determine whether
the argument is not a text string. If the argument is not a text string, the function returns the
#N/A error. Otherwise, it returns the characters in reverse order.
The data type for the return value of the original REVERSETEXT function was String
because the function always returned a text string. In this revised version, the function
is declared as a Variant because it can now return something other than a string.
Returning an array from a function
Most functions that you develop with VBA return a single value. It’s possible, however, to write a
function that returns multiple values in an array.
Part IV deals with arrays and array formulas. Specifically, these chapters provide examples
of a single formula that returns multiple values in separate cells. As you’ll see, you
can also create custom functions that return arrays.
VBA includes a useful function called Array. The Array function returns a variant that contains
an array. It’s important to understand that the array returned is not the same as a normal array
composed of elements of the variant type. In other words, a variant array is not the same as an
array of variants.
If you’re familiar with using array formulas in Excel, you have a head start understanding the VBA
Array function. You enter an array formula into a cell by pressing Ctrl+Shift+Enter. Excel inserts
brackets around the formula to indicate that it’s an array formula. See Chapter 15 for more details
on array formulas.
The lower bound of an array created by using the Array function is, by default, 0.
However, the lower bound can be changed if you use an Option Base statement.
The following MONTHNAMES function demonstrates how to return an array from a Function
procedure:
Function MONTHNAMES() As Variant
MONTHNAMES = Array( _
“Jan”, “Feb”, “Mar”, “Apr”, _
“May”, “Jun”, “Jul”, “Aug”, _
“Sep”, “Oct”, “Nov”, “Dec”)
End Function