I believe the excel function will fill in each substring into a different column, right? If you consider the Excel lines as records and columns as fields, do you really want to create new fields?
I assume that you probably don't want to do that, but I assume that you want to create new records per substring in one field, so you get e.g. in a list box of that field a line per substring.
You could use subfield for that.
If you have loaded your table
recno() as RecID,
You could do something like:
subfield(Reason, ',') as ReasonSubs
Hope this helps,