yes create two property sets in your cell properties
"Add-ons Allowed" with conditions for either addons are allowed / roundnumber is =<5
"Add-ons Complete" with conditions for addons are completed / roundnumber is =>6
I would then just change the font colour in the during add-on cell set to the same as the background - effectively hiding the prizemoney but keeping the cell contents the same and the other conditions with a visible font colour.