Auto-Fill text box

Auto-Fill text box

I am trying to autofill a text box based on what I have chosen in the above lookup drop down box. This is linked to another form.

Form 1 - New Request Form - this has the fields Supplier and Manufacturer Code. Supplier is a lookup drop down field which gets its data from Form 2 (Suppliers form). Manufacturer Code is a text box which is supposed to autopopulate.

I would like to choose a supplier in the Supplier field and have the Manufacturer Code auto populate in the Manufacturer Code textbox, but it is not working. I have tried everything! 

This is the code I have:


    Suppliers  =  Suppliers_form  [ID == input.Supplier];
    input.Manufacturer_Code = Suppliers.Manufacturer_Code;


Please help!!!!