I run a report based on a slice:
AND([WEC]=TODAY(),ISBLANK([WorkShopComplete]))
If I test the slice it returns the correct information and omits the [WorkshopComplete] data if those rows contain anything so I know the ISBLANK is working through the slice.
However, with the report it ignores the ISBLANK([WorkshopComplete]) and returns data for [WEC]=TODAY() including rows where [WorkshopComplete] is blank or contains data.