Im pretty sure I've done this before but what I'm trying to do it populate a text field from the chosen result of a lookup field. 

This is the current code, Ive tried many but this is what I can remember. 

input.Nextjob = input.Which_Site_will_you_Attend_next; 

NextJob - Single Line 

Which_Site_will_you_Attend_next - Lookup Field 

I want to copy the result as shows in the lookup field which is primarily the client loaded from that form but linked to another form. I can use another field in the other form thats already text but still not working. 

this is the error I get 

Error at line number : 1 
Variable 'Single_Line' is already defined of data type 'STRING' but trying to update 'BIGINT' data type

Any help would be awesome!