using variables as field names in Stored Procedures

[Craig]

hey all,

i can't seem to figure out how to specify a field name in a stored procedure using a variable:

for example, in a table which has a unique entryID, then 5 fields which are called f1,f2...f5.

i would like to be able to do this:

CREATE PROCEDURE changeStat(IN entryID INT, IN fieldName VARCHAR(10), IN value INT)
BEGIN
UPDATE userStats SET fieldName = value WHERE tableName.entryID = entryID;
END//

creating this stored procedure is fine, but when it's run i get this error:
Unknown column 'fieldName' in 'field list'.

in reality the table i am using is a lot bigger than 5 fields, and i would prefer not to hardcode a huge switch statement with the correct statement being called for the fieldName which is passed in.

cheers,
Craig