Change Object on associations

When i do a change object  , i can do it fine on attributes of the changing entity. but when i try to change on association in changing entity , then it does not allow me. what i need to take care that this works.  ex: entity1 has 3 attributes(col1, col2,col3), i can change object them and change col1 and col2 fine. but entity1 is associated with entity2 on col3 so when i choose the association to change that value, i cannot do it.. i get error : the microflow expression is of type string , but should be of type reference to modulename.entity2 any ideas how to change the association value in change object .
1 answers

In mendix an association is not done with attribute (value), so if you want to link entity 1 to entity2, you have to  retrieve the entity2 (or create it), and make a change object of entity1, and put the entity2 inside the association