Increment field value on REPLACE

I have done this successfully with an UPDATE statement before but not a REPLACE.

I am saving favourite items in a mysql table when a user has checked out.

Table Favs is:

USER (int)
ITEM (int)
COUNT (int default 0)

The SQL I am trying is :

REPLACE INTO favs (user,item,count) VALUES ('1','3', count + 1)

although it does not throw any errors it does not seem to increment the value either.

Is this possible? Thank you.