Hi,
Sorry for a late reply. Ok, now if u can do writing characters to LCD, no matter it is a 4 line or 8 line interface.
First of all, if u r using assembly language programminbg it is very difficult to do ur job (Plez clarify). I think u r having a 2 line display. If so u have 0x80 as ur first line address and 0xC0 as ur second line address. If u r going to display a menu, for example; "Display settings" and u have an "Enter" key for entering that menu then u have to display "Display settings" in first line, then, when an enter key is pressed u can simply display the sub menu in second line. If u have more than one sub menus , then use two keys for up and down function. If a down key is pressed, simply display " "(16 spaces) then display ur second sub menu and so on.
Really, it is a teadious task
Good luck