In that case, use a SKIPIF field that tests the values of the two fields. For example:
{SKIPIF{MERGEFIELD Total_Previous}={MERGEFIELD Total_Current}}
where 'Total_Previous' and 'Total_Current' are the field heading names in your csv file.

Note: The field brace pairs (ie '{ }') for the above example are created in the body of the document via Ctrl-F9 (Cmd-F9 on a Mac) - you can't simply type them or copy & paste them from this message.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]