Translate lookup field value into single line field

Translate lookup field value into single line field

Hi All,

I have two separate applications: app_one and app_two

app_one contains a form with a single line text field "email_one"
app_two contains a form with a lookup field "lookup_email" and a single line text field "translate"

When a user selects a value from the lookup I would like the value to appear in "translate" 

I've attempted the following with no joy:

hello= app_one[ID = input.email_one];
input.translate = hello.lookup_email;

Can someone tell me what I'm doing wrong? 

Thank you in advance.