Can a field auto populate in a secondary form from a primary form?

Can a field auto populate in a secondary form from a primary form?

I have form1 (aka: proposals) which collects...
project number
customer name
sales rep
& more...
 
form2 (aka: orders) needs to have some of the same fields auto-populate when an existing project number is selected from a look-up...
customer name
sales rep
 
IN SHORT:
What script or how else can a field auto-populate the 'customer name field' of form2 with the existing data in the 'customer name field' of form1?
 
Nathan