Assuming that you are using a command button to close the 4th form, add this code to the Click Event:
DoCmd.Close acForm, "frm1stForm"
DoCmd.Close acForm, "frm2ndForm"
DoCmd.Close acForm, "frm3rdForm"
DoCmd.Close acForm, "frm4thForm"
If I understand your post correctly, this should provide a solution.
Let me know if it works.
Larry De Laruelle
larry1de@yahoo.com