When you use the line in the example code:

rst.Index = "PrimaryKey"

:you are telling the recordset what to use as the primary key. If the primary key of the table you are connected to contains multiple columns the index property of your recordset will contain the multiple columns as well. Keep in mind that the Index property is an array so when you go to use the seek method, you have to pass an array that contains all of the necessary columns that make up the primary key.