Merci pour votre réponse.
J'ai trouvé ceci pour ceux qui s'intéresse:
Public Class ucgain
Declare Function CreateRoundRectRgn Lib "gdi32" (ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long, ByVal X3 As Long, ByVal Y3 As Long) As Long
Private val As Integer
Declare Function SetWindowRgn Lib "user32" (ByVal hwnd As Long, ByVal hRgn As Long, ByVal bRedraw As Boolean) As Long
Private Sub ucgain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim rndrectangle
Dim frmApplique
Try
rndrectangle = CreateRoundRectRgn(1, 1, 390, 27, 15, 15)
frmApplique = SetWindowRgn(Me.Handle, rndrectangle, True)
Catch ex As Exception
MessageBox.Show(ex.ToString)
End Try
End Sub
J'ai réussi à faire ce que je voulais.
Bien à vous.