If your object_1, object_2, object_3 etc. are different objects, then what you are asking is impossible. You can't refer to object by its name in expressions.
One workaround is to put all objects into a family, define an instance variable "type" on this family, set different type for each object. Then in your events you can pick family member by type and access its value.
You can create a function "GetObjectValue" that takes type parameter, picks that object from the family and returns object value. Then you will be able to use this function in expressions.