Update Primary Key

[Maynard]

Is there a way to change the value of a primary key? I
want to add a year value to the record number. The record
numbers start over each calendar year and I need to
identify them as to avoid having duplicates. Each record
has a number [INCNUMBER] which is the primary key for the
record, and a date [DATE]. I tired the [INCNUMBER]update
value in the update query:
"datePart("yyyy",[DATE])& [INCIDENTNUM]
All that is returned is the INCIDENTNUM with out the date
part.