I have a chart, created by an Excel macro, with data derived from a
named sheet. I'm trying to modify that chart in VBA to reference a
different sheet with a different number of lines. Simple enough,
except that the chart has custom error bars, and there appears to be
no way to retrieve the formula associated with those error bars. Excel
obviously keeps a formula for these error bars - I can see it through
"Format Error Bars" in the UI - but I don't see it anywhere in a
watch. Anyone know how I can get to - and modify - the formula for
error bars? Here's my code thus far:

Option Explicit

Const SEARCH_DIR = "F:"

Public Sub Weekly_Charts()
Dim wb As Workbook
Dim sh As Variant
Dim cht As ChartObject
Dim ser As Series
Dim strFormula As String
Dim i As Integer
Dim j As Integer
Dim iDayRows As Integer
Dim iWeekRows As Integer
Dim errb As ErrorBars

Set wb = Workbooks.Open(SEARCH_DIR &
"base_n_year_by_province_2008.xls")
For Each sh In wb.Sheets
Select Case sh.Name
Case "Data_Sheet"
iDayRows = sh.UsedRange.Rows.Count
Case "Weekly_Data"
iWeekRows = sh.UsedRange.Rows.Count
End Select
Next sh
For Each sh In wb.Sheets
Select Case sh.Name
Case "Data_Sheet"
Case "Weekly_Data"
Case Else
Set cht = sh.ChartObjects(1)
cht.Activate
For Each ser In ActiveChart.SeriesCollection
ser.Formula = WorksheetFunction.Substitute
(ser.Formula, "Data_Sheet", "Weekly_Data")
ser.Formula = WorksheetFunction.Substitute
(ser.Formula, iDayRows, iWeekRows)
If ser.HasErrorBars Then
Set errb = ser.ErrorBars
' Now what???
End If
Next ser
sh.ChartObjects(2).Delete
sh.ChartObjects(2).Delete
End Select
Next sh
Workbooks.Close
Set wb = Nothing
End Sub

(..and how come, if I define sh as Woksheet, I get a type mismatch on
"For Each sh In wb.Sheets"??)