How to know Status is allowed to Update or Not

Hi Experts,

I try hard to find the solution but couldn't get correct answer.

I am updating status using FM 'CRM_STATUS_CHANGE_EXTERN' , problem is if status is not update(becoz wrong code) still FM give sy-subrc is 0.

I have Header GUID , status profile and Status to be Update. In ABAP report how can we find the next status(to be update) is allowed or not.

For Example:

support there are 5 status like: E0001 , E0002, E0003, E0004, E0005.

If current status is E0003 , next allow status would be E0004 , E0005, but not allowed E0001, E0002. (In shot way it can not move back)

Is there any FM which give the information next change status is possible or not.

Please please Help.

Thanks,

Raj.