To get that exact layout you would have to create a custom UserForm. You can get a similar effect with a much easier InputBox.
To get that border you would have to use a single cell table. Here's a start (I'm on holiday from Today)
Sub Add_Text()
Dim strText As String
Dim osld As Slide
strText = InputBox("Enter Text")
'NOTE THIS WILL NOT WORK IN SHOW MODE
Set osld = ActiveWindow.Selection.SlideRange(1)
With osld.Shapes.AddTable(1, 1)
With .Table.Cell(1, 1)
.Shape.Fill.Visible = False
.Shape.TextFrame.TextRange = strText
.Shape.TextFrame.TextRange.Font.Color.RGB = vbBlack
With .Borders(ppBorderTop)
.Visible = True
.Weight = 2
.ForeColor.RGB = vbBlack
End With
With .Borders(ppBorderBottom)
.Visible = True
.Weight = 2
.ForeColor.RGB = vbBlack
End With
End With
.Width = 200
.Left = 10
.Top = 10
End With
End Sub