The AddItem method simply appends (or inserts) an item in a string delimited
by semicolons. So if you AddItem "Tom", then "Dick", then "Harry", your
RowSource string will be "Tom;Dick;Harry".
You can use the Split function to morph this string into an array of three
strings, then use your favourite sort algorithm to sort the array, then
finally use the Join function to recreate a delimited string:
"Dick;Harry;Tom".