Medpack,

Thanks for the response.
Unfortunately I can not post the entire sheet due to it's proprietary nature. However, here is what info i can give:
There is a data sheet, and several charts. Each chart has an activation macro (code from one is shown below) that formats the chart to fit the entered data. The data sheet also has an activation macro that restores the formulas that the code below removes. Currently when I switch from the data sheet to the any chart the first time, the chart activation macro runs all the way through, but at some point has changed the EnableEvents to false. As a side note (not sure of the relevance) - this workbook was created in office 2007.

Private Sub Chart_Activate()

Check = Validate_Data(2)

If Check = "Yes" Then

Sheets("Thinking").Visible = True
Sheets("Thinking").Select
Application.ScreenUpdating = False


'Remove Chart Protection
Sheets("Trim & Viscosity Curve").Select
Sheets("Trim & Viscosity Curve").Unprotect

'Set max Range on the Primary X-Axis
ActiveChart.Axes(xlCategory).MaximumScale = Range("Q_MAX").Value * 1.05

'Set Max range on the Secondary X-Axis
ActiveChart.Axes(xlCategory, xlSecondary).MaximumScale = Range("Q_MAX").Value * 1.05 / 4.4028675

'Set max Range on the Y-Axis
n = Range("n").Value
ActiveChart.Axes(xlValue).MaximumScale = 500 * n

'Set Y-Axis Major Unit
ActiveChart.Axes(xlValue).MajorUnit = 50 * n

'Set Y-Axis Minor Unit
ActiveChart.Axes(xlValue).MinorUnit = 10 * n

'Set max Range on the secondary Y-Axis
m = Range("m").Value
'in order to auto scale the secondary y axis for the NPSH curve, un comment the next line and comment out the following line
'ActiveChart.Axes(xlValue, xlSecondary).MaximumScale = m * 50
ActiveChart.Axes(xlValue, xlSecondary).MaximumScale = 100

'Set secondary Y-Axis Major Unit
ActiveChart.Axes(xlValue, xlSecondary).MajorUnit = m * 5

'remove Core Data Protection
Sheets("Core Data").Unprotect

'Remove Chart warning
Sheets("Core Data").Range("MWarn").Value = ""

'Clear all zeros from original curve NPSH data
For Each c In Range("NPSH").Cells 'Worksheets("Core").
If c.Value = 0 Then c.ClearContents
Next

'Clear all zeros from viscosity curve NPSH data
For Each c In Range("VNPSH").Cells 'Worksheets("Core").
If c.Value = 0 Then c.ClearContents
Next

'Reactivate sheet and Chart Protection
Sheets("Core Data").Protect DrawingObjects:=True, Contents:=True, Scenarios:=True
Sheets("Core Data").EnableSelection = xlUnlockedCells
Sheets("Trim & Viscosity Curve").Protect DrawingObjects:=True, Contents:=True, Scenarios:=True

Sheets("Trim & Viscosity Curve").Select
Sheets("Thinking").Visible = False
Application.ScreenUpdating = True

End If

End Sub