Another thing I have in mind: For certain attributes there are additional so called local attributes (attributes which are not stored in the db), which holds the "previous" value of this attribute. These attributes have the trailing name part "_prev". So what's about the idea to create such an attribute, and then use it in your notification condition to check, if the attribute has changed.
I don't know if one is able to create a "local" attribute in wsp. So here is an example of a site/mods/majic/*.maj file to create such a "_prev" attribute for the attribute "zmyattr" of the cr factory. It has to be of the same data type as the original one (STRING, DATE, SREL ...) :
OBJECT cr {
ATTRIBUTES Call_Req {
zmyattr_prev LOCAL STRING { DERIVED_PREVIOUS zmyattr ; } ;
};
};
hope that helps, ... and works