A Simple Filtered Lookup
From Lookup:
var lookupItem = new Array;
lookupItem = crmForm.all.new_lookup1.DataValue;
alert(lookupItem[0].id);
alert(lookupItem[0].name);
var searchVal = lookupItem[0].name;
crmForm.all.new_lookup2.additionalparams = 'search=' + searchVal.replace("&","%26").replace("+","%2b");
From Picklist:
var searchval = new Array;
searchval = crmForm.all.new_picklist1.SelectedValue;
crmForm.all.new_lookup1.additionalparams = 'search=' + searchVal.replace("&","%26").replace("+","%2b");