Update a row that has a UNIQUEID

[jazz59]

Hi everyone.
I understand that an advantage of using Row ID is to prevent duplicates; what if I want to edit (in this case, change values of certain columns) an already existing row? When I try to do this, an error message appears: "There is already a row with the key (*[Row ID]*)". 
How can I update previously inserted data that has a Row ID? Do you I need to delete it and create a new entry?
Thank you.

[jazz59]

Just to give a bit more context: by clicking on the "edit" action button, data is updated. However, the data i'm trying to update was retreived from a different form (through "LINKTOFORM"); in order to update both forms, I'm trying to update the row by refilling the 1st form, then save the 2nd form - the error message appears in this last step (that is, when I try to save the 2nd form)