There is no "lag" type function for macro variables - suggest you track "n" unique macro variable values as "MyMacroVar1" through "MyMacroVar99" or however many you need to run through.
It would be more useful to explain what you are attempting to accomplish for beneficial feedback from the forum subscribers, particularly how you start the process, then each iterative step, working through to the final objective / output.
Scott Barry
SBBWorks, Inc.