Macro causing Excel to freeze - intended to hide cells with zero value

Hey all,

My apologies in advance if this has been covered elsewhere, but I am very new to macros and am in need of a quick resolution to this.

I have pieced together the following code (see below) that is intended to hide cells with zero values. Essentially, it is in an invoice spreadsheet that shows the number of employees who worked a certain interval of time, i.e. the recipient could look at it and say there were X cashiers working from 2pm to 5pm, Y cashiers from 3pm to 5:30pm, Z cashiers from 3:30pm to 7pm, so on and so forth for every possible 15 minute increment of time.

As you can imagine, this involves a lot of cells (about 36k rows) that often don't have a value, and I need a way to hide them when the value is zero. This particular string of code has worked in the past, but for some reason it will only work once. If I try and run it a second time, Excel freezes up and I'm essentially screwed.

Here's the code. I'm running Excel 2010 on Windows 7. Again, I'm very new to this and have only made it this far by Googling and copy/pasting bits of code.

Private Sub Worksheet_Change(ByVal Target As Range)
Application.Calculation = xlCalculationManual
Application.EnableEvents = False
Application.ScreenUpdating = False
Dim c As Range
For Each c In Range("A2:A36490")
If c.Value = 0 Then
Rows(c.Row).Hidden = True
Else
Rows(c.Row).Hidden = False
End If
Next c
Application.Calculation = xlCalculationAutomatic
Application.EnableEvents = True
Application.ScreenUpdating = True

End Sub

Any help would be greatly appreciated! Thanks in advance!