I don't know if its because I'm using version 7 but my scripting guide doesn't contain the section mentioned. I did find the answer although its not a single command like I had hoped.
There is a function called nTable() which gives me the number of open data tables and then I can use a for loop to get a list of table names.
table_names={};
for(i=1,i less than =nTables(),i++,insertinto(table_names, Data Table(i)<