For starters, you can add a text field with an auto-enter calculation of:
OCTET1& "." & OCTET2& "." & OCTET3& "." & OCTET4
You can set a Unique Values validation on this field and also use it to determine what value combinations have already been used.
From there, reasearch the term "dwindling value list" to find examples of how to set up a value list that automatically drops out values that have been previously selected.
And you can find an example of such in this file along with many other methods for selecting values: