According to this Dell website for Latitude CSx you are correct, they would not work. http://support.ap.dell.com/support/edocs/systems/pmac2cm/en/en_ug/specs.htm#memory
Ram in india http://cgi.ebay.in/a-data-ddr2-256mb-laptop-notebook-ram-533mhz-memory_w0qqitemz390138528124qqcmdzviewitemqqptzlh_defaultdomain_203?hash=item5ad611817c#ht_5250wt_716