Word Document Properties

Listing 7-7
Displaying a Form
Public Sub ShowAForm()
‘ Use the Show method to show a form.
‘ You can perform other tasks using a modeless form.
ButtonDemo.Show vbModeless
‘ A modal form requires that you complete the task 
‘ with that form before you proceed to other tasks.
NumericText.Show vbModal
End Sub
The problem that many developers face is deciding between a modal form
and a modeless form. Always use a 
modeless
form if you want to display
other forms or perform other tasks while the current form is displayed. Use a
modal
form when you want to ensure that any tasks for the current form are
complete before you display another form.
The example code shows both kinds of forms. You can try to select the
ButtonDemo
form, but you won’t be able to do it. The 
NumericText
form
insists that you complete tasks with it before you do anything else. As soon
as you finish working with the 
NumericText
form, the program completes.
VBA displays modeless forms and essentially forgets about them.
Validating user input
Always validate user input. The main source of security problems and many
types of application errors is user input. If the user doesn’t provide the 
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Chapter 7: Interacting with the User
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correct input, your program doesn’t run no matter how much effort you put
into it. In addition, many security exploits rely on poor program validation. A
buffer overrun,
one of the well-known causes of security problems, is simply
a failure to check input. Validating user input means that you should do the
following:
Always ensure that the input uses the correct data type.
Always check the range of numeric information.
If you want numbers
between 1 and 5, don’t let the user input anything else.