ms access query update

I am trying to set an ms access query to update different fields in a table based on different values in another table.  If i run it the update below if erases the previous set values. Is there a way to nest these expression so that they only execute the condition when is true.

UPDATE [table1] INNER JOIN table2 ON [table1].field1 = table2.field1
  SET
     table1.field10  = IIF(table2.fieldz=17,-1),
     table1.field11 = IIF(table2.fieldz=18,-1),
     table1.field12 = IIF(table2.fieldz=19,-1),    
     table1.field13 = IIF(table2.fieldz,30,-1,IIF(table2.fieldz,44,-1,IIF(table2.fieldz,141,-1)))
 
WHERE table1.fieldB=2 ;