When using forms you can apply autofilters, and formfilters, but you can not 
create a custom filter easily to f.i. enter a start and end date.

It would be *very* usefull to be able to add unbound controls on a form (say 
StartDate and EndDate) and then have the datasource on the form use those 
controls to filter the records, i.e. 

select * from atable where Date > :StartDate and Date < :EndDate

It appears to my from the SDK (see DevelopersGuide chapter 13.5.1 section 
Parameters) that this can be done by adding the controls to some list of 
listeners (using com.sun.star.form.XDatabaseParameterBroadcaster) so that they 
get resolved when the query runs (done by 
com.sun.star.form.XDatabaseParameterListeners).

However, it is unclear what code to use to do that, and the SDK mentions at 
this time it can not be done from Basic.

To me it seems that unbound controls on the form should *always* by listening 
to queries that require input. Why else would they be there?

Also it is not clear (to me) from the SDK if the unbound control is listening 
to queries run by other forms or if a special syntax is needed to access a 
control on another form (like MS Access does).