Adding record into form with lookup field (by custom action function)

Adding record into form with lookup field (by custom action function)

I created a function to load a new record with data from one row of a report. The form I'm trying to add a record into uses a lookup field (integer). The lookup field is mandatory. When I execute the function, I get an error: "Reference field unit_code not having the value 465,202" (the 465202 is the integer I'm trying to enter into this field, but the error is showing it with a comma, could this be the problem?)

Must a lookup field always be entered by hand?