Yes, you will need to create a table and a form. Create a table called tblPsWrd and make one field DateCreated(Date Datatype). Then on your Switchboard or StartUp form in the On_Open event write some code to test weather the desired amount of time has past since the password was created. Something like this
dim myRec as Dao.recordset
det myrec=currentdb.openrecordset("tblPsWrd")
myrec.moverfirst
if DateDiff('d',myrec.fields("DateCreated"),date())=30 then
docmd.openform("frmChangePassword')
end if
frmChangePassword would be the form you made to chage the password of the database and update the date in the tblPsWrd.