Hi,
[MATCH]database_field_name||$uri->getValue('search_field_name')[/MATCH] should do the trick, just use two date fields and set appropriate matching on them, then you can use both in query - of course aou will also need to construct the right query with it, but this is something you unfortunately need to be familiar with to be able to use use this field. You can see how you resulting query looks if you turn on debugging in the search type.