* VB-CODE (2)
Tip 96: Centering a Form over Another Form

May 29, 1995

You can position a form so it appears centered within another form.
This article explains how to center a form within its parent form.
This same technique can be applied to centering controls such as
Picture Box controls over other controls.

Centering Forms in Visual Basic
When developing an application in Visual Basic®, you may need to
position a form so it is centered over another form. You can position
a form in this way by using Visual Basic's Left, Top, Height, and
Width properties.

The Left property defines the position of the form's left edge and the
Top property defines the position of the form's top edge. In the same
manner, the Width and Height properties define how wide and high the
form is. It is easy enough to center a form on a container by
calculating the width and height of the form and dividing that value
by two to center it within the control.
To center a form within a parent form, take the width of Form1 and
Form2, subtract these two values, and divide the result by two. Next,
add Form1's width to the result to determine the position of Form2's
left edge within Form1. This will center Form2 horizontally within

In the same manner, you can center a form vertically within another
form by using the Top and Height properties of each form, dividing by
two, and setting Form2's Top property to the result.

Example Program
This program shows how to center a form over another form. After you
run this example program by pressing the F5 function key, click the
Command Button. The program displays Form2 centered over its "parent,"

 1. Create a new project in Visual Basic. Form1 is created by default.
 2. Add a Command Button control to Form1. Command1 is created by
 3. Add the following code to the Click event for Command1:

Private Sub Command1_Click()
    CentreFormWithParent Form2, Form1
End Sub

 4. From the Insert menu, select Form to create a second form. Form2
    is created by default. Change this form's size so it is smaller
    than Form1.
 5. Create a new function called CreateFormWithParent. Add the
    following code to this function:

Sub CenterFormWithParent(aForm As Form, aParent As Form)
    aForm.Left = aParent.Left + (aParent.Width - aForm.Width) / 2
    aForm.Top = aParent.Top + (aParent.Height - aForm.Height) / 2
    If (aForm.Left + aForm.Width) > Screen.Width Then
        aForm.Left = Screen.Width - aForm.Width
        If aForm.Left < 0 Then aForm.Left = 0
    End If
    If (aForm.Top + aForm.Height) > Screen.Height Then
        aForm.Top = Screen.Height - aForm.Height
        If aForm.Top < 0 Then aForm.Top = 0
    End If
End Sub