Shopping Cart Unique OrderNumber?

Here's a good Shopping Cart question to bennifit many who are stuck using random OrderNumbers.

I need to select the largest OrderNumber from one table, increment 1, then insert the new larger number into a second table

Q. How can I combine the two seperate SQLs below into one classy and usefull SQL?


SELECT 1+ MAX(col_OrderNumber) FROM FirstTable

INSERT INTO SecondTable (col_OrderNumber, col_FirstName, col_LastName)
                           VALUES ( '" OrderNumber,'" + FirstName.ToString() + "', '" + LastName.ToString() + "')