How do I save data of a 2 level transaction in Genexus 3 whenever a parent attribute changes value referenced in child formulas

I have a 2 level transaction in Genexus Evolution 3 Upgrade 10 internet tomcat 6 java 1.6 responsive. After confirming an update, it first modifies an attribute in the parent level and some attributes in the child level records which have a redundant formula of a percentage factor on the parent attribute, but then it appears a message in the viewer such as " was modified" and it does not save the data. The parent attribute value is changed thru a call in the rules with an "on BeforeValidate" trigger event