Your English is very good, but let's use the word "table" in place of "database" to avoid possible confusion. "Database" can mean different things in different contexts when talking about FileMaker solutions. We can call your first table "WorkTable" and your second table "SearchTable".
You can certainly add a table to serve that purpose, but do you know that you do not need that table to get the list of records for a selected company and range of dates?
If you want to see all records for "Acme Construction" from 3/1/2013 to 3/8/2013, you can:
Enter find mode
Enter "Acme Construction" in the company name field.
Enter 3/1/2013...3/8/2013 in the Date field
Perform the find
and you now have a list of all Acme Construction records in that range of dates.
If you still want to add that second table, you can use this relationship:
SearchTable::Company Name = WorkTable::Company Name AND
SearchTable::DateStart < WorkTable::Date AND
SearchTable::DateEnd > WorkTable::Date
With this relationship, you can list records from WorkTable on the SearchTable layout in a portal or you can use the Go To Related Records script step to bring up the matching WorkTable records on the WorkTable layout.