Calculation in update query

  I want to be able to update a value in a table to the existing value plus
or minus a value set in a variable without having to read in the current
value first.  Any help would be appreciated.

  The desired action could be described like the following query:

  UPDATE tablename SET columnname='currentvalue_in_column +-
value_in_variable' WHERE key='key_variable';



Thank You,
Christopher A. Goodfellow
Director of Information Technology
Tealuxe, Inc.
Phone: 508 520 7887 ex:22
Fax: 508 528 8999
www.tealuxe.com
tea for all