Command Dialog Flags Problem

I have used Command Dialog to allow the user to navigate through all the different directories
I want the user to be able to select all the files in a desired directory

I know that the Flag cdlOFNAllowMultiselect(&H200) allows you to do this. But I cannot use it
This is the code from the Browse Command Button

CommonDialog1.ShowOpen
CommonDialog1.Flags = cdlOFNAllowMultiselect
Text1.Text = CommonDialog1.FileName

Does anybody know how to use the Flags for Command Dialog
Thanks in advance