I have a work flow, whenever the stage move from New opp to anything but closed lost, their will be a date stamp. however, my workflow is change the time when created, and every time it’s edited. I need the date to be stamp not changing every time when people edit it.
How should I do that? It seems like the one I use PRIORVALUE is only supporting "created, and every time it’s edited" as the evaluation rule.

Here is my work flow: 
ISPICKVAL(PRIORVALUE( StageName ),"1. New Opportunity") && NOT(ISPICKVAL( StageName,"Closed Lost")) && NOT(ISPICKVAL( StageName,"Closed - Unqualified")) && NOT(ISPICKVAL( StageName,"1. New Opportunity"))&& NOT(ISPICKVAL( StageName,"2. Discovery Call"))&& NOT(ISPICKVAL( StageName,"Closed - Professional"))

I have a work flow, whenever the stage move from New opp to anything but closed lost, their will be a date stamp. however, my workflow is change the time when created, and every time it’s edited. I need the date to be stamp not changing every time when people edit it.
How should I do that? It seems like the one I use PRIORVALUE is only supporting "created, and every time it’s edited" as the evaluation rule.

Here is my work flow: 
ISPICKVAL(PRIORVALUE( StageName ),"1. New Opportunity") && NOT(ISPICKVAL( StageName,"Closed Lost")) && NOT(ISPICKVAL( StageName,"Closed - Unqualified")) && NOT(ISPICKVAL( StageName,"1. New Opportunity"))&& NOT(ISPICKVAL( StageName,"2. Discovery Call"))&& NOT(ISPICKVAL( StageName,"Closed - Professional"))