Delete Duplicated rows

http://help.lockergnome.com/office/d...ct1003548.html
above is cross-link to First post. Sorry I didn't find this forum first. I am somewhat green with everything but basic excel.
I have a spreadsheet with columns A through F. Column "C" is an invoice # and is listed multiple times, depending on the number of items billed on this invoice. I'm trying to delete all multiple copies of this invoice leaving only the first instance of each (the first entry has the total sale). I found a macro on a forum from a while back and it will delete my duplicate invoices if I insert my invoice # to Column "A", but it get's my other columns out of sync. I think this macro was written for a two column spreadsheet. Here is the Macro that almost works:

Sub DeleteDupes() 
Dim Iloop As Integer 
Dim Numrows As Integer 

'Turn off warnings, etc. 
Application.ScreenUpdating = False 
Application.DisplayAlerts = False 

Numrows = Range("A65536").End(xlUp).Row 
Range("A1:B" & Numrows).Select 
Selection.Sort Key1:=Range("A1"), Order1:=xlAscending, _ 
Key2:=Range("B1"), Order2:=xlAscending, Header:=xlYes, _ 
OrderCustom:=1, MatchCase:=False, Orientation:=xlTopToBottom 
For Iloop = Numrows To 2 Step -1 
If Cells(Iloop, "A") + Cells(Iloop, "B") = Cells(Iloop - 1, "A") + _ 
Cells(Iloop - 1, "B") Then 
Rows(Iloop).Delete 
End If 
Next Iloop 

'Turn on warnings, etc. 
Application.DisplayAlerts = True 
Application.ScreenUpdating = True 
End Sub

I'm not familiar enough with Macros to know how to adapt this. Any help would be greatly appreciated.
Marv