Something like this
ItemCrossReference.RESET;
ItemCrossReference.SETCURRENTKEY("Cross-Reference Type","Cross-Reference Type No.");
ItemCrossReference.SETFILTER(
"Cross-Reference Type",'%1|%2',
ItemCrossReference."Cross-Reference Type"::Customer,
ItemCrossReference."Cross-Reference Type"::" ");
ItemCrossReference.SETFILTER("Cross-Reference Type No.",'%1|%2',SalesHeader."Sell-to Customer No.",'');
IF PAGE.RUNMODAL(PAGE::"Cross Reference List",ItemCrossReference) = ACTION::LookupOK THEN BEGIN
VALIDATE("Cross-Reference No.",ItemCrossReference."Cross-Reference No.");
END;
You need to use Vendor Posting Group Record and Page instead of Item Cross Reference and apply necessary filter on Vendor Posting Group based on your selection