Code optimization to avoid multiple file open calls

Hello Excel Forum!

I have a function that opens a file on my network drive and compares a string to the values of the cells in A column. Here is the function:

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I call this function in the following snippet of my macro:

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My situation is this: The "For Each cell" loop is going through a range of 30-100 cells and it calls my function for each cell in the range. That means we're opening and rereading/reparsing the file 30-100 times. Surely, there is a more efficient way for me to do this where I open the file once, compare the values in the A column of my active spreadsheet to the values in the A column of the "Flagged.csv" file and if any value is found in both files to pop up a MsgBox. Any ideas? Here are some sample files for you to work with. Flagged.csv Deposit.csv

Thank you in advance!

Mind = Blown

Thank you AlphaFrog! It works perfectly and has a few bits for me to study and learn from!