Fetch original custom field value in behavior

[Vimalraj]

Hi,

I'm trying to add a year to a date field based on custom field value in behavior. 

For ex., 

if(issue.getCustomFieldValue(ConditionAgreed) != originalIssue.getCustomFieldValue(ConditionAgreed) {

def expirydate = getFieldByName("Expiry Date")

def expirydatevalue = expirydate.getValue() as Date

def revisedexpirydate = expirydatevalue.plus(365)

expirydate.setFormValue(revisedexpirydate.format('MM/dd/yyyy'))

}

However, I could not get it working. Please help 

Thanks

--Vimal