This feature is not supported in any of crystal decisions' products, and the only thing I can offer is workarounds.
If the parameter field is for a fairly static value, such as customers (most companies will not add more than a few new customers per week), you can probably get by with deleting and re-importing the default values once a week or so.
If the parameter is for a very non-static value such as Sales Order number (with potentially hundreds of new values per day) this obviously will not work.
On the internet I recently found a "picklist creator" for Crystal Reports for just this type of situation at www.infotrain.com. I have not experimented with this yet but I think it would be possible to use this application in to automatically update the default values for parameters.
If you are adept at using VB and Crystal, I believe a you could create a valid workaround with VB as well.