In order to generate sequential numbers in your action list you need to use variables. An example of this along with a loop would be:
LOOP A START COUNT=1000000
ASSIGN VARIABLE <filevar SEQUENTIAL 1 1000000>
1 get http://2.2.2.2/filename<APPLY filevar>
LOOP A STOP
For detailed information on the use of loops and variables, please see the online help in the Avalanche GUI ( Accessed using the F1 key)