Ahhh...

ThEiMp, that will put a msgbox in the center of the screen and not in the right corner of the window as the OP asked...

kpmsivachand, okay, new standard exe project>add command button>add code...
Code:
Option Explicit

Private Sub Form_Load()
Me.Left = 0
Me.Top = 0
End Sub

Private Sub Command1_Click()
Load Form2
Form2.QuarterSizeMessage Me, "this is a test"
Form2.Show vbModal, Me
End Sub
Now add another form (Form2) and on it add a label (label1)>add code...
Code:
Option Explicit

Public Sub QuarterSizeMessage(WhoCalled As Form, TheMessage As String)
Me.Width = (WhoCalled.Width * 0.25)
Me.Height = (WhoCalled.Height * 0.25)
Me.Left = (WhoCalled.Left + WhoCalled.Width) - Me.Width
Me.Top = (WhoCalled.Top)
Label1.Left = 0
Label1.Top = 0
Label1.Height = Me.Height
Label1.Width = Me.Width
Label1.Caption = TheMessage
End Sub
Run>click>see

Good Luck