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Session 9 — Working with Text 117

Listing 9-1 also includes a procedure named TestIsNumber that lets you test the
IsNumber function. The code in this procedure uses the InputBox function to prompt the
user to enter an integer number. The IsNumber function then tests whether the text
entered by the user is, in fact, a number. The loop repeats until a valid number is entered.
It would be a good programming exercise for you to modify the IsNumber
function so it also accepts numbers with a decimal point or a leading minus
Note sign.
To run this demonstration, follow these steps:

1. Open the VBA Editor.
2. Open the code-editing window for one of the modules in the Project Explorer win-
dow. Because this program does not interact with a worksheet, it does not matter
which module you use.
3. Insert the code from Listing 9-1 into the module.
4. Place the editing cursor anywhere inside the TestIsNumber procedure.
5. Press F5 to run the program.

In addition to pressing F5, you can run a VBA procedure by clicking the Run
Sub button on the toolbar, or by selecting Run Sub from the Run menu.
Tip

The Chr Function

This function returns the character that corresponds to a specific numeric code. The syntax is:
Chr(code)

The code argument is the numeric code of interest. The function returns a string con-
taining the corresponding character. If code is out of range, an error occurs.

Extracting or Modifying Parts of Strings

The VBA functions that are covered in this section are used when you need to extract or
modify part of a string.

The Left and Right Functions
These functions extract a specified number of characters from either the left or the right
end of a string. The syntax is:
Left(string, length)
Right(string, length)