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Conditional Formatting for Matrix Symmetry

I’ve been looking into Dataframe conditional formatting, and I want to be able to highlight specific cells if they don’t match cells in another column and row.
Essentially, I want to check if a matrix someone put into the Dataframe is skew symmetric, meaning indices (i,j) would equal (j,i) for row i and column j. I want to highlight the pair of cells in red if they aren’t equal, and the diagonal if it isnt 0. I wasn’t able to figure out how to reference specific values from other columns as I iterated through columns, but I did see that I could write an external function to do it. Is that my only option?