This sounds like you want to make the value(s) available in param 5 and 6 dependent on the values selected in param 4 - is this correct ?
i.e. if you select "all" in param 4, then either show "all" and nothing else in param 5 and 6 OR show "all" as well as other values in param 5 and 6. If "all" is not selected in param 4, then show everything except all in param 5 and 6.
To do this sort of thing, I would create datasets for param 5 and for param 6 - these datasets would be used to populate the available values for param 5 and param 6. Each of these datasets would have the value selected in param 4 as a parameter to the dataset. Using that parameter, the logic for returning the "all" value can be made conditional on whether has been selected in param 4.