Word Document Properties

Chapter 4: Storing and Modifying Information
09_046500 ch04.qxp 12/5/06 5:54 PM Page 97

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Using Boolean values to make decisions
The 
Boolean
type is the easiest to use and understand. This type is used to
indicate yes or no, true or false, and on or off. You can use this type to work
with any two-state information. It’s commonly used to represent data values
that are diametrically opposed. Chapter 5 shows how to use 
Boolean
values
to make decisions. Listing 4-10 shows several conversion techniques that you
can use with 
Boolean
values.
Listing 4-10
Making Decisions with Boolean Values
Public Sub BooleanCheck()
‘ Create a Boolean data type.
Dim MyBool As Boolean
‘ Set MyBool to True
MyBool = True
‘ Display the native value.
MsgBox “MyBool = “ + CStr(MyBool), _
vbOKOnly, _
“Native Value”
‘ Display the numeric value.
MsgBox “MyBool = “ + CStr(CInt(MyBool)), _
vbOKOnly, _
“Numeric Value”
‘ Make MyBool equal to a number. Only the number
‘ 0 is False; everything else is True.
MyBool = CBool(0)
MsgBox “MyBool = “ + CStr(MyBool), _
vbOKOnly, _
“Converted Numeric Value”
End Sub
The code begins by declaring a 
Boolean
variable and setting its value. As with
numeric variables, you can assign a 
Boolean
variable directly to a string as
long as that’s the only thing that you do. When working in a mixed data type
environment, such as the one shown in the code, you must use the appropri-
ate function (such as 
CStr
) to perform the conversion.
The 
Boolean
type isn’t numeric — it’s logical . . . simply a decision value.
You can convert it to a number, as shown in the example code. The value is
always 
-1
for 
True
values and 
0
for 
False
values.
VBA also lets you convert a numeric value to a 
Boolean
type by using the
CBool
function shown in the code. Any value that you store in the 
Boolean
,
other than 
0
, equates to 
True
. Converting the 
Boolean
back to a number
still shows 
-1
for 
True
values and 
0
for 
False
.
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