Call Edit screen from Add screen

Call Edit screen from Add screen

Hi,

Just a quick question, if this is possible :
 
In the field's On User Input, I created some functions to check if the record already exists, and then would display the value for rest of the fields on the form. The problem is, when I click on Submit, it adds a new record instead of updating the existing record.
 
How do I make sure it _Updates_ the record instead of inserting it?
- OR -
How do I add a link to the Edit screen, so I can ask : "Record Exist, click here to Edit instead"
 
 
 
Thanks for the direction.
 
 
 
Peter