How to hide multiple columns at once in Excel 2007 using vba - excel

Question

I would like to hide multiple columns inside an excel worksheet. This works pretty fine using:
ActiveSheet.Range("R10:CO10").EntireColumn.Hidden = True
"R10" is the first and fix column to hide. The second column and all columns between to hide will be dynamically determined depending on it´s date value.
Sample Coding:
Private Sub Worksheet_Activate()
Dim c As Range
Dim start As String
Dim ende As String
start = "R10"
ende = "CO10"
Dim d As Date
d = Date
For Each c In Range("R10:HU10")
If c = (d - 8) Then
ende = **how to assign???**
End If
If c = (d - 7) Then
Application.Goto c, True
End If
Next c
'ActiveSheet.Range(**"start:ende"**).EntireColumn.Hidden = True
End Sub
Row 10 holds date values and I would like to hide all columns which dates are older than 7 days and I can´t find any hints about hiding multiple columns using variables or with column identifier or the number of the column etc.
The use of variables ends up in runtime error 1004.

Answer 1

As Scott pointed out, my first answer was not complete. You can use the following function:
Function GetColChars(col As Integer) As String
Dim coldown As Integer 'Column Countdown
Dim colrem As Integer 'Coumn Value Remaining
Dim colname As String 'Temporary String value for column name
Const alphanums = 26
Const aposition = 64
coldown = col
colname = ""
While coldown > 0
colrem = coldown Mod alphanums
If colrem = 0 Then colrem = 26
newchar = Chr(64 + colrem)
colname = newchar & colname
coldown = Int((coldown - 1) / alphanums)
Wend
GetColChars = colname
End Function
Then call the function to get the column letters:
ende = GetColChars(c.column)

Answer 2

I have tested Scotts solution approach and finally got it working. In that case that some other people will struggle with the same problems, getting a working solution, here is my solution:
Private Sub Worksheet_Activate()
Dim lastDateRangeColumn As Range
Dim givenDateRange As Range
Set givenDateRange = ActiveSheet.Range("R10:HU10")
Dim firstDateRangeColumn As Range
Set firstDateRangeColumn = ActiveSheet.Range("R10")
Dim todaysDate As Date: todaysDate = Date
For Each tempDateRangeColumn In givenDateRange
If tempDateRangeColumn < (todaysDate - 7) Then
Set lastDateRangeColumn = ActiveSheet.Range(tempDateRangeColumn.Address)
End If
If tempDateRangeColumn = (todaysDate - 7) Then
Application.Goto tempDateRangeColumn, True
End If
Next tempDateRangeColumn
Dim firstColumnNumber As Long
Dim lastColumnNumber As Long
firstColumnNumber = Range(firstDateRangeColumn.Address).Column
lastColumnNumber = Range(lastDateRangeColumn.Address).Column
Dim rangeToBeHidden As Range
Set rangeToBeHidden = Range(Cells(1, firstColumnNumber), Cells(1, lastColumnNumber))
rangeToBeHidden.EntireColumn.Hidden = True
End Sub