Cross Validation acros Flexfields

Hello,

We have two flexfields setup on Opportunities in Oracle Sales (12.1.3.1) as below -

attribute1, valueset1 (Start Date)
attribute2, valueset2 (End Date)

The attribute1 is designated as Start Date and attribute2 is designated as End Date.

How can I a validation on valueset2 so the date > valueset1, i.e. user can only enter an End Date which is greater than Start Date and not vice versa.

I tried creating valueset2 with Value Validation as “Special” and using a custom SQL when defining the custom validation, but it seems that Special value validation does not work on framework pages… it works only on Forms.