Checking If A Sheet Exists In An External Closed Workbook - vba

Question

I want to test whether certain sheets in the current workbook exist in another closed workbook and return a message saying which sheet/s are causing errors.
I prefer not to open/close the workbook so I'm trying to change the formula in a random cell to link to the workbook of filepath (fp) to test whether the sheet exists.
I've tested this with a dummy sheet that I know doesn't exist in the other workbook and it works but when I have more than one sheet that causes errors I get an "Application-defined or object-defined error". On the second iteration I believe the way the error handling is written causes the crash but I don't exactly understand how that works.
The code I've got is:
Sub SheetTest(ByVal fp As String)
Dim i, errcount As Integer
Dim errshts As String
For i = 2 To Sheets.Count
On Error GoTo NoSheet
Sheets(1).Range("A50").Formula = "='" & fp & Sheets(i).Name & "'!A1"
GoTo NoError
NoSheet:
errshts = errshts & "'" & Sheets(i).Name & "', "
errcount = errcount + 1
NoError:
Next i
Sheets(1).Range("A50").ClearContents
If Not errshts = "" Then
If errcount = 1 Then
MsgBox "Sheet " & Left(errshts, Len(errshts) - 2) & " does not exist in the Output file. Please check the sheet name or select another Output file."
Else
MsgBox "Sheets " & Left(errshts, Len(errshts) - 2) & " do not exist in the Output file. Please check each sheet's name or select another Output file."
End If
End
End If
End Sub
Hopefully you guys can help me out here, thanks!

Answer 1

Here's a slightly different approach:
Sub Tester()
Dim s As Worksheet
For Each s In ThisWorkbook.Worksheets
Debug.Print s.Name, HasSheet("C:\Users\blah\Desktop\", "temp.xlsm", s.Name)
Next s
End Sub
Function HasSheet(fPath As String, fName As String, sheetName As String)
Dim f As String
f = "'" & fPath & "[" & fName & "]" & sheetName & "'!R1C1"
HasSheet = Not IsError(Application.ExecuteExcel4Macro(f))
End Function

Answer 2

Just an update for Tim's Function for error Handling:
VBA:
Function HasSheet(fPath As String, fName As String, sheetName As String)
On Error Resume Next
Dim f As String
f = "'" & fPath & "[" & fName & "]" & sheetName & "'!R1C1"
HasSheet = Not IsError(Application.ExecuteExcel4Macro(f))
If Err.Number <> 0 Then
HasSheet = False
End If
On Error GoTo 0
End Function

Answer 3

Sub Tester()
MsgBox (Not IsError(Application.ExecuteExcel4Macro("'C:\temp[temp.xlsm]Sheetxyz'!R1C1")))
End Sub