43 regex get the string in a defined middle

Code:
Imports System
Imports System.Text.RegularExpressions
Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim mCollect As MatchCollection = Regex.Matches("sjlfhal{yes}djklafh{yess}", "(?<={).*?(?=})", RegexOptions.IgnoreCase)

        For Each m As Match In mCollect
            MsgBox(m.Value)
        Next
    End Sub
End Class

' output : yes yess