How to modify the dialogfield when other dialogField is changed using X++ in ax 2009


I'm trying to fetch bom name when we change Bom id in look up field from Item master form > Bom >lines> Create bom form

it is using dialog 

How i can modify bom id field to show name for that selected bom id during run time?


  fieldNumber = dialog.addField(typeid(BOMId),"@SYS22298");
    fieldName       = dialog.addField(typeid(Name),"@SYS6303","@SYS50975");