Thank you for enquiry.
Unfortunately OpenFileDlg (the object returned by Utilities.NewOpenFileDialog), does not support multiple selection of files.
If you are using Formativ 2.0, the Forms Editor includes TOpenDialog on the Dialogs tab of the Component Palette. TOpenDialog has a similar interface to OpenFileDlg but is more powerful, with additional properties. The following is quoted from the help file on TOpenDialog’s Files property:
Files is a string list that contains each selected file name with its full directory path. (To let users select multiple file names, set the ofAllowMultiSelect flag in Options.) Use properties and methods for string lists to traverse this list of files and read individual items.
I hope this helps.