Charlotte,
I believe you need three fields.
[Current Value]
[Current Value Sync]
[Previous Value]
The automations need to fire in a sequence that will ensure you do not lose the information when the Save occurs.
When [Current Value] changes, the first automation needs to write the value of [Current Value Sync] to [Previous Value]
When [Previous Value] changes, the second automation writes the value of [Current Value] to [Current Value Sync]
[Current Value Sync] is a hidden field that you do not let any Users or other automations access.
------------------------------
Don Larson
Paasporter
Westlake OH
------------------------------