Capturing previous info from a field

np,

A Pipeline is your easiest solution and most reliable because it will work on Forms as well as Grid Edit or even imported records. Create a fields to hold the previous values, obviously.

Then create a Pipeline to Trigger on Record Updated, specify it should trigger on any of those three fields being changed. Then also specify those three fields to be used in subsequent steps.

Then the second and last step of the pipeline will be Update Record and write the previous values of those fields into your set of three fields you created to hold the previous values.  The tricky part which is not that tricky once you know it is the syntax for capturing the previous value. 

The easiest way to do that is to first populate those three fields with the selection of the regular field so for example Member ID.

Then look at the box where you put that and there is this symbol that looks like this at the top right corner </>.  Click that and observe that it will toggle back-and-forth between the friendly looking label and the somewhat less friendly looking syntax that would look like this 

 {{a.Member_ID}}

Simply carefully hand edit that field to read like this 

{{a.$prev.Member_ID}}

And do the exact same thing with any other fields you want to track the previous value of. 

... Having answer the question you've asked, I will point out that it is not really what you need because what happens if the user changes their Member ID or name once again.  

The best way to do this really is to have a child table of an audit log and what you would do is do the same kind of thing but instead you will create a child record into a table that you will have created for your membership record called audit trail or something like that.  If it's just a few fields your tracking like those three then you can have three fields on the record and you were just write the previous values into those three fields. 

The other thing nice about that is it automatically gets date stamped with [Date Created].  If you'd like you could also create a user field and populate who edited the membership record into that field so you know not only when the change was made and what the change was but who made it.