Private Sub MouseEnter(sender As Object, e As System.EventArgs) Handles _
      Button1.MouseEnter, Button2.MouseEnter, Button3.MouseEnter, _
      Button4.MouseEnter, Button5.MouseEnter
        Dim btn As Button = DirectCast(sender, Button)
 
        btn.Font = New Font(btn.Font, FontStyle.Bold)
 
    End Sub
 
    Private Sub MouseLeave(sender As Object, e As System.EventArgs) Handles _
      Button1.MouseLeave, Button2.MouseLeave, Button3.MouseLeave, _
      Button4.MouseLeave, Button5.MouseLeave
        Dim btn As Button = DirectCast(sender, Button)
 
        btn.Font = New Font(btn.Font, FontStyle.Regular)
    End Sub

EALA FREYA FRESENA

Public Class Form1
    Dim button As New Button
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        For Each Button As Button In Me.Controls
            AddHandler Button.MouseEnter, AddressOf Enter
            AddHandler Button.MouseLeave, AddressOf Leave
        Next
    End Sub
 
    Shadows Sub Enter(sender As Object, e As EventArgs)
        Dim myFont As System.Drawing.Font
        myFont = New System.Drawing.Font("Sans-Serif", 8.5, FontStyle.Bold Or _
          FontStyle.Italic)
        sender.font = myFont
    End Sub
    Shadows Sub Leave(sender As Object, e As EventArgs)
        Dim myFont As System.Drawing.Font
        myFont = New System.Drawing.Font("Sans-Serif", 8.5, FontStyle.Regular)
        sender.font = myFont
    End Sub
End Class