Set 'previous' value using workflow

In SharePoint Designer 2013 Workflow, Although you can wait until a specific field changed. but Unfortunately, you can't catch the Field old value, because of the Workflow is executed after the item is updated.

The Practical workaround solution is:

Create an Event Receiver on Item Updated or 'Item Updating' to get the old and new value.

• To get old value on Item Updated

       string before = properties.BeforeProperties[properties.ListItem.Fields["yourfield"].InternalName].ToString();    
  

• To get new value on Item Updated

       string after = properties.AfterProperties[properties.ListItem.Fields["yourfield"].InternalName].ToString();
  

Note: in case you are using Item Updating you can get the old value and new value as the following:

• The old value use properties.ListItem
• The new value use properties.AfterProperties

Your current system allows you to detect the change.

• If the two fields are equal, then this particular field wasn't changed,
• if they are different then it was changed. Then,
• if they're different, update the previous field to the current value so that it can detect the next change. Good. Add another field called "historical value" (or rename your current field, as my naming suggestion here is not great).

When a change is detected, before setting your previous field, set the historical field to the current value of previous.

So, given a new record with a developer of Amy, before the workflow runs, the values will be:

dev: amy
prev: (blank)
hist: (blank)

after the workflow:

dev: amy
prev: amy
hist: (blank)

Then, after changing it to mark, before the workflow:

dev: mark
prev: amy
hist: (blank)

Since dev != prev, the condition is met, and prev will be copied into hist, and then the current value will be copied into prev. So after the workflow runs, you'll have:

dev: mark
prev: mark
hist: amy

Of course, M.Qassas has a nice solution as well that doesn't require additional fields. This answer requires the extra field, but doesn't require code.