Custom function will not update automatically (settings are set to auto calculations!) - vba

Question

I have a custom function that detects if a cell is bold
Function isBold(cellBold)
If cellBold.Font.Bold = True Then
isBold = 1
ElseIf cellBold.Font.Bold = False Then
isBold = 0
Else
isBold = 0
End If
End Function
Puts 1 in a cell if the reference cell is bold and 0 if it is not bold
This works well and all the first time around but if I make the reference cell bold the number stays at 0. Automatic calculations are on, the only way for the function to calculate again is to retype the function

Answer 1

Adding Application.Volatile to the top of your function will make it auto update when the workbook change event is fired.
Function isBold(cellBold)
Application.Volatile
If cellBold.Font.Bold = True Then
isBold = 1
ElseIf cellBold.Font.Bold = False Then
isBold = 0
Else
isBold = 0
End If
End Function
This will not help you if you just bold a result but you can add an event to the sheet you're working on
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Calculate
End Sub
If both of these things are in place, your formula will update every time you select a different cell which may work well enough for you. However, I suggest using this method with caution because if you have a very large number of formulas this could slow things down.
-Edit- This should fix the copy paste issue.
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim col As Range
For Each col In ActiveSheet.UsedRange.Columns
col.Calculate
Next
End Sub

Answer 2

OK, So I'll be the first to admit this is not an ideal solution, and is pretty hackish. But i think it will fix your solution.
After adding the volatile line to your code as so:
Function isBold(cellBold)
Application.Volatile True
If cellBold.Font.Bold = True Then
isBold = 1
ElseIf cellBold.Font.Bold = False Then
isBold = 0
Else
isBold = 0
End If
End Function
First Change your Workbook_Open to this:
Private Sub Workbook_Open()
Sheets("Sheet1").rngLastCell = Range("A1").Address
Sheets("Sheet1").fntLastCell = Range("A1").Font.Bold
End Sub
Then on the worksheet you are working with (In my example Sheet1) Add this to the Worksheet function:
Option Explicit
Public fntLastCell As Boolean
Public rngLastCell As String
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If Sheets("Sheet1").Range(rngLastCell).Font.Bold <> fntLastCell Then
Calculate
End If
Sheets("Sheet1").rngLastCell = Target.Address
Sheets("Sheet1").fntLastCell = Target.Font.Bold
End Sub
Now to have it work you must Save then close, Then re open your worksheet.
This works by setting 2 global variables each time you select a new cell.
a Boolean variable that states weather the Last Cell selected WAS PREVIOUSLY Bold or not. And a String Variable that references that same Cell. So, you can now check the Bold state of the cell you exited (when it was entered) against the Current Bold State of the cell you just existed and if there was a change it will calculate the workbook. Otherwise nothing will happen.
Hope this works and helps,
Cheers