Pass down SQL using parameters

[synapsevampire]

I fear I already know the answer, but is there any way to get reasonable performance from Crystal by passing through SQL when you need to do the following?

Select multiple values from a drop down for a parameter, or if they select the choice of 'All', this part of the where would be eliminated or be set to retrieve all rows.

It appears that as soon as an if is used, the SQL isn't passed.

Is there a cheat, such as concatenating the SQL or some such?

<he said hopefully>

And if there isn't a cheat, does anyone know how difficult it is to customize Crystal Enterprise to allow me to pass through values to a stored procedure rather than use the default parameter gathering method in Crystal?

Crystal seems impossibly bad when there will be multiple choices, or all, am I missing something important here, or do most Crystal users NOT make multiple selections into a parameter and care about the resulting performance?

Thanks in advance