saving edited record to another table

I am working with a demo of phprunner. having some difficulty saving a record to an audit table everytime the record is edited in the main table.
my main table is mto_main. my audit table is mto_audit. whenever i edit a record in mto_main i want to create a new record in mto_audit. 3 of my field names are: userID, InquiryDate and MemberID. The structure of both tables is the same. I have tried the following:
function BeforeEdit(&$values, $where)

{
//** Insert a record into another table ****

global $conn;

$strSQLInsert = "insert into mto_audit (userID, InquiryDate, MemberID) values (userID, InquiryDate, MemberID)";

db_exec($strSQLInsert,$conn);
return true;
}
any help would be appreciated,
thank you