I have seen a post here rather identical to my question. Allow me to elaborate:

Generic information:
- I will be getting one new sheet with data for every month that passes,
they are thus named as months.
- Sheet1, labelled "overview", has a summary of all subsequent sheets.

Specific information:
- All subsequent sheets contain a row of headings, and then a list of 100
text entries.
- The overview sheet is to display a complete list of all entries in
subsequent sheets, but these entries will inevitably repeat themselves in
some cases.
- Thus, what I need, is for "overview" to run a formula in each cell of
column A which will check for new/duplicate entries in subsequent sheets, and
then return the text of any of those sheets if that entry is not a duplicate
already found in the "overview" list.

This has been run by alot of people, so this would be my last resort. I am
novice to advanced user with Excel, and am really just wondering if I will
need to write up a small piece of VB code to solve this or if Excel itself
has formulas/code which will solve this mind-boggler for me.