I have normal excel document
consisted of 2 columns A and B.
In each columns there are 4000 rows.
In each row is url adress in form: http://www.studiotatjana.com

I want new list of urls in column C which is sum of values in column A and B.
So there will be 8000 urls in column C.

But there needs to be only one rule.

If value in one row of 4000 row in column A is
identical to any value in any row in column B then
that value do not go to colum C.

I want that if one url adress can be fund in column A and B
that that url is deleted and do not go to column C.

All values in colum A are diferent.
And all values in column B are diferent.
But there may be 1000 identical adreses and i dont want them to come in
columnt C

Please can you help with some funkction or formula
and I am new user so can you give me step by step explenation how to
like: file - open etc.

Best regards and thank you
Ivanko Perišić