How do I switch between windows in the active workbook inside a Macro.

I have a Macro that reformats how ever I need it to do that in Window 2 of
the active workbook. I cannot have it file specific. It needs to take the
active filename and drop it into the formula.

Here is what I have so far. This works but I cannot figure out how to get
the active filename.:

Windows("FS Side Vent.xls:2").Activate
Sheets("Print").Select
Range("OrderNo").Select
Cells.Select
Selection.EntireRow.Hidden = False
For I = 1 To 800
Range("A" & I).Select
If ActiveCell.Value = "0" Then
Selection.EntireRow.Hidden = True
Else
End If

Next I

Range("OrderNo").Select