Check if field = null and populate populate counter

Please help....
I have 2 tables:
Table 1: suppliers

Table 2: supplier_info
This is what I want to achieve. Users goes to the EDIT page via the suppliers table and enters there company information.

At this point the supplier_info table is blank. When the users clicks SAVE, data is populated to the new table supplier_info.
Should the user go back to the EDIT pages and amend there personnel information and click SAVE, I do not want the supplier_info table to be populated with duplicate records.
Here's the code:
global $conn;
if ($values["checkpopulate"] == null){
$strSQLInsert = "insert into supplier_info (email, company, country) values('".$values["email"]."','".$values["company"]."', 'Germany')";

db_exec($strSQLInsert,$conn);
$strSQLInsert = "insert into supplier_info (email, company, country) values('".$values["email"]."','".$values["company"]."', 'France')";

db_exec($strSQLInsert,$conn);
$strSQLInsert = "insert into supplier_info (email, company, country) values('".$values["email"]."','".$values["company"]."', 'Sweden')";

db_exec($strSQLInsert,$conn);
}else{

($values["checkpopulate"] = "1");

}
return true;
I have managed to populate the supplier_info table when the user clicks SAVE via the Supplier EDIT page. Initially, the checkpopulate field is set to NULL. However, i cannot get the logged in users field checkpopulate to be updated to 1.
Please Help and thanks in advance
Lisa