Windows 7批处理：执行ECHO的输出

Question

I want a batch file to run a command like this:

start Firefox "http://www.billboard.com/charts/hot-100?chartDate=2012-12-01"

I want it to update the date before running, so that tomorrow the executed command will look like this:

start Firefox "http://www.billboard.com/charts/hot-100?chartDate=2012-12-02"

I have devised a batch file with these two lines:

set BBURL=start Firefox "http://www.billboard.com/charts/hot-100?chartDate=%date:~10,4%-%date:~4,2%-%date:~7,2%"
echo %BBURL%

These lines give me the command I want, updated each day as shown above. But they don't actually run the command. So (1) is there a better way to do this and (2) in any event, for future reference, how can I redirect or execute the "echo %BBURL%" output so that it runs as a command?

Cheers!

PS The other part of the question, which I forgot to add: how can I subtract, from the year, a number like 40, to get the Billboard listing for 40 years ago today?

Answer 1

Can't you just do:

set BBURL=start Firefox "http://www.billboard.com/charts/hot-100?chartDate=%date:~10,4%-%date:~4,2%-%date:~7,2%"
%BBURL%