Running macros on multiple windows

I'm running a macro that has worked on previous computers (windows xp and office 2000), I'm now using windows 7 and office 2007.

The macro is designed to cycle through a number of windows, the amount defined using an inputbox function, taking data from each file and putting it into a summary file. Currently, the macro is only working for the first window and wont cycle through. The program reads as follows:

Sheetall = InputBox("Number of worksheets to be analysed?")
      Sheettot= Val(Sheetall)

      For sheetnow= 1 To Sheettot
              Windows(sheetnow+ 1).Activate

                  (here is the main body of the macro, which is working fine)

      Next sheetnow

Can anyone please help??