MYSQL insert statement help

[harry boy]

Hi, sorry if this is in the wrong place.
I have a SQL statement that does not seem to be inserting values into my database.
I have a table called MainTable with columns FAMILY_ID and PERSON_NAME. I want to insert a name into the row only if the FAMILY_ID column equals a certain string value.

The below is not working (value I want to insert is not getting inserted)

string command1 = "INSERT INTO MainTable (PERSON_NAME) VALUES ('" + sName + "') WHERE FAMILY_ID = ('" + sFamilyID + "')";
oleDbCommand.CommandText = command;
oleDbCommand.ExecuteNonQuery();

Does anyone know whay??