Validation using WBS element creation date

Hi,

I am facing problem in WBS validation ;

I need to check only those WBS elements which are created after one specific date : for example 01.01.2013,

Validation should not apply on WBS elements which have been created before 01.01.2013:

For this i am using PRPS-ERDAT > 01.01.2013 , but i am getting ABAP Dump when i am creating new WBS element as it is using temp data .