I see what you mean by removing the .RowFormat function and when I use "HighlightRed", the behavior is exactly as I would expect. Without .RowFormat, I see "HighlightRed" in the far right column of every generated row.

I'm using =IF(1, "HighlightRed", "") which I assume logically asks the question "If any cell in this row has a non-zero value the apply the "HighlightRed" style.

Now when I change "HighlightRed" to "FormatHidden": If I remove .RowFormat, I do see "FormatHidden" in the far right column of every generated row as expected. But, with .RowFormat, the strange thing is that the rows are not hidden at all. What happens is that columns A,B&C are blanked out while the rest of the columns remain unchanged. "HighlightRed" applies to All columns in the row but "FormatHidden" seems to only apply to columns A,B&C and would be more aptly called "FormatBlank".

Does this make sense?

Thanks.

Richard