I think the problem is not that you do not have a range, but that DSUM only
works on a list or database. That is "a list of related data in which rows of
related information are records, and columns of data are fields. The first row
of the list contains labels for each column."

The only workaround I can think of would be to copy the data to a new sheet -
making sure it met the criteria for a database, do the DSUM, and then hide, or
delete the sheet.

Or, possibly, do separate DSUMs on each of the parts of the list and add them
together.