A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
I'm not sure it will do what you want, but here is a version that does not cause an error message:
Sub August2013()
If Range("17:49").EntireRow.Hidden = True And _
Range("57:123").EntireRow.Hidden = True Then
Range("17:49.57:123").EntireRow.Hidden = True
Range("16:16,50:56").EntireRow.Hidden = False
ElseIf Range("17:49").EntireRow.Hidden = False And _
Range("57:123").EntireRow.Hidden = False Then
Range("17:49").EntireRow.Hidden = False
Range("16:16,19:19,22:22,25:25,28:28,31:31,34:34," & _
"37:37,40:40,43:43,46:46,49:56").EntireRow.Hidden = True
End If
End Sub