Highlight Duplicates between Sheet1 and Sheet2, ignoring duplicates already in Sheet1

I have been searching for a formula how I can highlight duplicate data between two different worksheets but ignoring duplicates on one of the worksheets. I have tried a few formulas and macros but not getting the results I want. Hoping someone here is able to help.

For a better understanding, I have a database which has multiple worksheets (eg. sheet1, sheet2, etc...), in the first worksheet it has 10k+ rows, and multiple columns with different kinds of data, lets call this worksheet "Sheet1". The other worksheets are not really important. I will create a new worksheet and give it a name, then I will copy and paste some data into this worksheet which will expand across several columns and rows, lets call this worksheet "Sheet2". In Sheet1 I want to focus only on column "I" and in Sheet2 I will want to look at columns A thru Z (or entire worksheet).

I am looking for a way to highlight duplicates between Sheet1 and Sheet2, but I do not want to highlight duplicates already in Sheet1 column I, just highlighting the duplicates found in Sheet2. Then highlight those in Sheet2 that were found to be duplicates.

Edit*
Solved with these formulas
=COUNTIF(Sheet1!$A:$Z,$I1)
=COUNTIF(Sheet1!$I:$I,sheet2!A1)