VBA Change error handling method during code execution - excel

Question

I have a macro, and part of the code is concerned with:
1) detecting if a column contains empty cells - if so filling them with some value
2) detecting if a column contains cells containing errors (such as N/A) and if so filling them with some value
Now if there are no error/empty cells in the column, the line that finds them gives a "Run-time error 1004 no cells were found".
I use error handling to skip this with GoTo.
Below is the code - the first error handling GoTo works perfectly, while the second gives the expected error, although there is Error handling GoTo set, that does not seem to work. Code with comments:
On Error GoTo EErrorOne
'depending on file I get, below line will generate error and code successfully skips to ErrorOne label
Workbooks(nazwawb).Sheets(szitnr).Columns(ktorepole).SpecialCells (xlCellTypeBlanks)
' code to be skipped
Workbooks(nazwawb).Sheets(szitnr).Columns(ktorepole).Select
Selection.SpecialCells(xlCellTypeBlanks).Select
Selection.Value = "Some Value"
' end of code to be skipped
EErrorOne:
' successfully skipped error line by now. Below line should set a new Error handling procedure.
On Error GoTo EErrorTwo
Workbooks(nazwawb).Sheets(szitnr).Columns(ktorepole).Select
' Below line generates an error but does not skip to EErrorTwo label as detailed in the current Error handling procedure
Selection.SpecialCells(xlCellTypeFormulas, 16).Select
' code to be skipped
Selection.SpecialCells(xlCellTypeFormulas, 16).Select
Selection.Value = "Some Value"
' end of code to be skipped
EErrorTwo:
' Below line should reset error handling procedure to normal for subsequent handling of other errors:
On Error GoTo 0
It seems that error handling procedure (GoTo specific label) is ignored, and instead, an error message is shown as if the error handling was reset to GoTo 0. How do I skip the second error?

Answer 1

You're not clearing your errors when they occur, just trying to jump over them and the code is wondering what's going on with the error.
As Chip Pearson says on his site:
When the first error is raised, execution transfers to the line
following Err1:. The error hander is still active when the second
error occurs, and therefore the second error is not trapped by the On
Error statement
and continues with
The Resume statement instructs VBA to resume execution at a specified
point in the code. You can use Resume only in an error handling
block; any other use will cause an error. Moreover, Resume is the only
way, aside from exiting the procedure, to get out of an error handling
block. Do not use the Goto statement to direct code execution out of
an error handling block. Doing so will cause strange problems with
the error handlers.
http://www.cpearson.com/excel/errorhandling.htm
The ideal way is to avoid the error in the first place - check the workbook exists before opening it, check the sheet exists in the workbook before trying to reference it and if an error occurs jump out of the main body of the routine, deal with the error and then jump back in again.
As an example:
Sub Test()
On Error GoTo ERR_HANDLE
'.... code ....
FAST_EXIT:
'Code to tidy up, clear references etc before finishing.
Exit Sub
ERR_HANDLE:
Select Case Err.Number
Case 1004
'Code to resolve error
'.
'.
'Resume - clear error, jump back to line that caused it.
'Resume Next - clear error, jump to line after the one that caused error.
'Resume FAST_EXIT - clear error and go to line label.
Case 92 'Do something else to resolve error.
Case Else
End Select
End Sub

Answer 2

Inside error handling routines, it seems as though defining new error handling routines won't work, unless you clear the previously set error routine (https://excelmacromastery.com/vba-error-handling/):
'...
EErrorOne:
On Error GoTo -1 'Clears error trap flag
On Error GoTo EErrorTwo 'Reset error handling
'...
Edit after accepted:
As was discussed in the comments, On Error GoTo -1 clears the error trap flag, while Err.Clear only clears the error.
The code below illustrates this by creating two errors and trying to trap them.
On Error Goto -1 allows the second error to be trapped by the On Error GoTo NextLabel line and the code jumps to the label when the error occurs.
Err.Clear keeps the first error live, so when the second error occurs the error message is displayed rather than the code jumping to the label.
Sub ClearErr()
Dim x As Long
Dim y As Worksheet
'Jump to label when "Division by 0" occurs.
On Error GoTo ErrorLabel
x = 1 / 0
Debug.Print x
ErrorLabel:
'On Error GoTo -1 'Next error is trapped.
Err.Clear 'Untrapped error on y=Worksheets(1)
'Jump to label when "Object Variable not set" occurs.
On Error GoTo NextLabel
y = Worksheets(1)
Debug.Print y.Name
NextLabel:
End Sub