This works in R4.6 and R5 and is documented in R5.
filepath := @Prompt([LOCALBROWSE]; "Select the file please:" "0");
The last parameter "0" means all files."1" = .nsf only and "2" = .ntf only.
Lotusscript
Dim ws As New NotesUIWorkspace
a = ws.OpenFileDialog( _
False, "Select csv file to be imported", ".csv", "C:\")
If Isempty(a) Then End
fileCSV = a(0) 'file location