Dim spos As Point
    Dim md As Boolean
    Dim lb As Boolean
 
    Private Sub Form1_MouseDown(sender As Object, e As _
      System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
        lb = e.Button = Windows.Forms.MouseButtons.Left
        spos = PointToClient(Cursor.Position)
        md = True
    End Sub
 
    Private Sub Form1_MouseUp(sender As Object, e As _
      System.Windows.Forms.MouseEventArgs) Handles Me.MouseUp
        md = False
    End Sub
 
    Private Sub Form1_MouseMove(sender As Object, e As _
      System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
        If md Then
            Dim mp As Point = PointToClient(Cursor.Position)
            Dim r As New Rectangle(Math.Min(spos.X, mp.X), Math.Min(spos.Y, _
              mp.Y), Math.Abs(spos.X - mp.X), Math.Abs(spos.Y - mp.Y))
            For Each c As Button In Controls
                If c.Bounds.IntersectsWith(r) Then
                    If lb Then
                        c.BackColor = Color.Red
                    Else
                        c.BackColor = Me.BackColor
                    End If
                End If
            Next
        End If
    End Sub

   Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) _
     Handles MyBase.Load
        For Each c As Button In Controls
            AddHandler c.Click, AddressOf Button_Click
        Next
    End Sub
 
    Private Sub Button_Click(sender As System.Object, e As System.EventArgs)
        Dim b As Button = CType(sender, Button)
        If b.BackColor = Color.Red Then
            b.BackColor = Me.BackColor
        Else
            b.BackColor = Color.Red
        End If
    End Sub

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