Run just one instance application

Public Function CheckInstanceOfApp() As Boolean
        Dim appProc() As Process
 
 
        Dim strModName, strProcName As String
        strModName = Process.GetCurrentProcess.MainModule.ModuleName
        strProcName = System.IO.Path.GetFileNameWithoutExtension(strModName)
 
        appProc = Process.GetProcessesByName(strProcName)
 
        If appProc.Length > 1 Then
            Return False
        End If
 
        Return True
 
    End Function