Fill field from other form

Fill field from other form

Hello,

I have this situation on one of my application: 

Form 1 (Opportunity - see pic1) is for manage the IT opportunities we have; here we have a field "opp_id" which is a numeric field we use to autogenerate the opportunity number; we have other fields like Country(Pais), Prime contractor, etc. 



Form 2 (Proyectos - see pic2) this form is for manage all the projects once an opportunity is won.

The fill-in is based the lookup field "Nro. de Oportunidad" on this form  which list all the opportunities from form1; when I select one Opp.  some other fields need to be filled.

My problem is in this form, I want to bring some data from form 1 (like Customer, Prime contractor).




Pic 3 is a View where you can see the expected values or info  for Customer & Prime contractor that I need to filled once an Opp. is selected on form2.




The code I have tried is on the user input of field Opp_nbr: (see pic4).

/ / Fill form Proyectos in order to Get Opp. number and fill customer and Prime Contractor fields
// based on form Opportunity
myopp  =  Opportunity  [ID == input.Opp_nbr];
input.Customer = myopp.Cliente.toString();
input.Prime_Contractor = myopp.Prime_Contractor.toString(); 





Now as you can see in Pic4 I have a problem of data Type (string/Bigint);  I put ToString() to correct that error message but the expected result is wrong because when I select the Opportunity Number ( see Pic5)  Customer & Prime Contractor are filled with incorrect information/values.

What I doing wrong?.

Please your help to fixed this problem.

Thanks.