Public Class ExBox
    Inherits TextBox
 
    Private myFocusBgColor As Color = System.Drawing.SystemColors.Window
    Private myPrevBackColor As Color = System.Drawing.SystemColors.Window
    Public Property FocusBackColor() As Color
        Get
            Return myFocusBgColor
        End Get
        Set(ByVal Value As Color)
            myFocusBgColor = Value
        End Set
    End Property
 
    Public Overrides Property BackColor() As System.Drawing.Color
        Get
            Return MyBase.BackColor
        End Get
        Set(ByVal Value As System.Drawing.Color)
            If Me.Focused Then
                myPrevBackColor = Value
            Else
                MyBase.BackColor = Value
            End If
        End Set
    End Property
 
    Protected Overrides Sub OnGotFocus(ByVal e As System.EventArgs)
        MyBase.OnGotFocus(e)
        myPrevBackColor = BackColor
        MyBase.BackColor = FocusBackColor
    End Sub
 
    Protected Overrides Sub OnLostFocus(ByVal e As System.EventArgs)
        MyBase.OnLostFocus(e)
        MyBase.BackColor = myPrevBackColor
    End Sub
End Class

Public Property FocusBackColor() As Color
        Get
            Return Me.txtBox.FocusBackColor
        End Get
        Set(ByVal Value As Color)
            Me.txtBox.FocusBackColor = Value
        End Set
    End Property