urgent creting dll

i have tow combo boxes in asp page and the values are coming form the database.
i have selected the value from the combo box and now i wnat to create the dll which will retrieve the values of other fields from the database and show rest of the vaules in database using the dll
how will i create the dll for fetching those values and the session values also which i need in next form
pl,s help me out
though it is possible to carete with asp but i wnat to create the dll ie a kind of interface

miss rajindar