the province needs to be repeated in the city list because it is link being used to create a relation ship.
the principle of dynamic dropdowns is to to filter related data.
For this to work you need to create a relationship between the value being posted from the parent list (the province) and the child recordset.
By listing the province for each city in the recordset, you have a piece of data that can be used to create the relation ship.
think of the province as the glue.
If you need further assistance, please post a copy of the page and a link where i can examine the page to troubleshoot.