Populate separate field from the drop down

Populate separate field from the drop down

I have a pick list for Mfg, when I choose the Mfg, I also want it to populate the Mfg Phone, Phone being a separate field.  

 Mfg
        (
            type  =  picklist
            values  =  manufacturers.Manufacturers.Manufacturer
            displayformat = [ Manufacturer ]
            allow new entries = true
            [
                displayname = "Manufacturer"
            ]
            sortorder  =  ascending
            searchable  =  true
            width  =  206px
            on update
            {
                if (input.Mfg  ==  input.Mfg)
                {
                    input.Phone = input.Phone;
                }
            }
        )