Function definition.

    SELECTIONDATA sel; // Define Address the slected line in the Disassembly window ( begin , End )
    GuiSelectionGet(GUI_DISASSEMBLY, &sel); // Get the value of sel(begin addr , End addr )
    duint pagesize = DbgMemGetPageSize(sel.start);  // get the page size of the section from the selected memory addr
    //Or use the following statement to get page base and size in one call.
    duint sctionbase = DbgMemFindBaseAddr(sel.start, &pagesize); // get the base of this section ( begin addr of the section )