Need to limit field criteria on a form by another field on the same form

Need to limit field criteria on a form by another field on the same form


In the criteria section of the dependant field, how to I refer to another field in the same form?
 
 
 
If you need more info...
 
Form name "Purchase_Order"
 
Field 1 "Vendor_Name"
Field 2 "Vendor_Account_Number"
 
 
Field 2 is a look-up field from table Vendor_Account_Number which in turn has a field "Vendor_Name"
 
I want to set the criteria for Fields 2 to only include records that the Vendor_Name == Vendor_Name on the current form
 
Thanks