Customize ArcMap Editing Function with ArcObject

Need to implement update point feature class attributes and delete point point feature. For the above mentioned one feature class, there is another point feature class which has relationship. The operation on each will affect the other one. For example, feature class A and B (both are related point feature class with one-many relationship) need functions as below: 1. Delete point in A will remove related points in B 2. Change attribute of A point will also change attributes of B points. And if the change is for ID field, need to check to make sure it is unified. 3. To add A point is already implemented. But I need new function: When add point A is on line C, need to assign one value of field automatically from line C's attribute value. I will provide the existing source code in C# and Personal or File based geodatabase. You can add new functions to the existing project or create a new project. ARCGIS version is 9.3.1 and C# or VB are both accepatable (though C# is preferred). Thanks.