خوب برای حل این مشکل دو راه داری
1- فکوس رو ببر یکی قبل از کامبو باکس به این شکل
Public Class Form1
Private Sub Form1_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyUp
If e.KeyData = Keys.Enter Then
SendKeys.Send("{Tab}")
End If
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Me.TextBox1.Focus()
End Sub
End Class
2 - که راه اصولی تر هست. رویداد keydown فرم رو حذف کن و برای هر یک از کنترل ها به غیر از button بنویس.
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Me.TextBox1.Focus()
End Sub
Private Sub TextBox1_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
If e.KeyData = Keys.Enter Then SendKeys.Send("{Tab}")
End Sub
Private Sub a_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles a.KeyDown
If e.KeyData = Keys.Enter Then SendKeys.Send("{Tab}")
End Sub
Private Sub b_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles b.KeyDown
If e.KeyData = Keys.Enter Then SendKeys.Send("{Tab}")
End Sub
End Class