A function is similar to a procedure but the main purpose of the
function is to accept a certain input from the user and return a value which is passed
on to the main program to finish the execution. There are two types of
functions, the built-in functions (or internal functions) and the
functions created by the programmers
The general
format of a function is FunctionName (arguments)
The
arguments are values that are passed on to the function. In this
lesson, you will learn two very basic but useful internal
functions of Visual basic , i.e. the MsgBox( ) and InputBox ( ) functions.
MsgBox ( ) Function
The objective of MsgBox is to produce a pop-up message box that prompt the
user to click on a command button before he /she can continues. This
format is as follows:
yourMsg=MsgBox(Prompt,
Style Value, Title)
The first argument, Prompt, will display the message in the message box. The
Style Value will determine what type of command buttons appear on the
message box, please refer Table 10.1 for types of command button displayed. The
Title argument will display the title of the message board.
Table 10.1: Style Values
| Style Value | Named Constant | Buttons Displayed |
| 0 | vbOkOnly | Ok button |
| 1 | vbOkCancel | Ok and Cancel buttons |
| 2 | vbAbortRetryIgnore | Abort, Retry and Ignore buttons. |
| 3 | vbYesNoCancel | Yes, No and Cancel buttons |
| 4 | vbYesNo | Yes and No buttons |
| 5 | vbRetryCancel | Retry and Cancel buttons |
We can use named constant in place of integers for the second argument to
make the programs more readable. In fact, VB6 will automatically shows up a list
of names constant where you can select one of them.
Example: yourMsg=MsgBox( "Click OK to Proceed", 1, "Startup Menu")
and
yourMsg=Msg("Click OK to Proceed", vbOkCancel,"Startup Menu")
are the same.
yourMsg is a variable that holds values that are returned by the MsgBox ( )
function. The values are determined by the type of buttons being clicked by the
users. It has to be declared as Integer data type in the procedure or in the
general declaration section. Table 10.2 shows the values, the corresponding
named constant and buttons.
Table 10.2 : Return Values and Command Buttons
Value |
Named Constant | Button Clicked |
| 1 | vbOk | Ok button |
| 2 | vbCancel | Cancel button |
| 3 | vbAbort | Abort button |
| 4 | vbRetry | Retry button |
| 5 | vbIgnore | Ignore button |
| 6 | vbYes | Yes button |
| 7 | vbNo | No button |
To make the message box looks more sophisticated, you can add an icon besides
the message. There are four types of icons available in VB as shown in
Table 10.3
InputBox( ) function
An InputBox( ) function will display a message box where the user can enter a
value or a message in the form of text. The format is
myMessage=InputBox(Prompt, Title, default_text, x-position, y-position)
myMessage is a variant data type but typically it is declared as string,
which accept the message input by the users. The arguments are explained as
follows:
- Prompt - The message displayed normally as a question asked.
- Title - The title of the Input Box.
- Default Text - The default text that appears in the input field where users can use it as his intended input or he may change to the message he wish to key in.
- x-position and y-position - The position or the coordinate of the input box.
Source: vbtutor WEB