The other day I found a handy script on Cisco EEM scripting community that can automatically archive the running-config if a a change has been made to it.
The archive feature must be configured first and you should also define an EEM variable for the script to work.
The script use the “Configuration Replace and Rollback” IOS feature to know if a change has been made by comparing the running-config the previous archive. If any differences the device will archive the config and it will be listed as most recent in the output of show archive.
Here is the link to the TCL script from Cisco: Archive_Config_if_Changes.tar.gz