Error if cancel or close input box. I want to exit sub.

If you use the application input box then you could test for a cancel or X click as follows:

Sub Test()
i = Application.InputBox("Enter number")
if i = False then
   MsgBox "User cancelled"
elseif len(i) = 0 then
   Msgbox "Nothing entered"
else
   MsgBox "Something entered"
End If
End Sub

If you don't want to use the application inputbox you can achieve the same as follows:

Sub Test2()
i = InputBox("Enter number")
if (StrPtr(i) = 0&) then
   MsgBox "User cancelled"
elseif len(i) = 0 then
   Msgbox "Nothing entered"
else
   MsgBox "Something entered"
End If
End Sub

Thanks ByteMarks! Definitely what has to be done but I've managed to make a complete mess of it when incorporating it into my existing code;

PHP Code: 

Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
    If Not Intersect(Target, Range("I11:I2010")) Is Nothing Then
        
        
        'When item is not marked as collected
        If ActiveCell.Value = ChrW(&H2713) Then
            
           SerialNo = Application.InputBox("Please enter Serial #:")
           If SerialNo = False Then
           MsgBox "Please enter Serial # to mark this item as not collected"
           ElseIf Len(i) = 0 Then
           MsgBox "Invalid Serial #"
           Else
           With Sheets("Lost Property Log")
           .Unprotect
           fRow = Application.Match(SerialNo, .Columns(3), 0)
           If Not IsError(fRow) Then
           .Cells(fRow, 9).Value = Cells(Target.Row, 9).Value
            ActiveCell.ClearContents
            .Protect
            End With
            End If
            
            
            

         'When item is marked as collected
           Else
           SerialNo = Application.InputBox("Please enter Serial #:")
           If SerialNo = False Then
           MsgBox "Please enter Serial # to mark this item as collected"
           ElseIf Len(i) = 0 Then
           MsgBox "Invalid Serial #"
           Else
           With Sheets("Lost Property Log")
            .Unprotect
            fRow = Application.Match(SerialNo, .Columns(3), 0)
            If Not IsError(fRow) Then
            .Cells(fRow, 9).Value = Cells(Target.Row, 9).Value
            ActiveCell.Value = ChrW(&H2713)
            .Protect
            End With
            End If
        
        
        
        
    End If 


So what I was hoping the code says is:

User double clicks cell >

1. If the cell is currently blank then serial number box appears and user enters serial number (if user clicks cancel or x or leaves blank then appropriate message appears and sub is ended) > serial number is found on LostPropertyLog and cell on LostPropertyLog and active cell get ticked.

2. If the cell has a tick already then serial number box appears and user enters serial number (if user clicks cancel or x or leaves blank then appropriate message appears and sub is ended) > serial number is found on LostPropertyLog and cell on LostPropertyLog and active cell get cleared.

But I'm getting 'End if without Block If' errors and I can't work out where I'm missing my Ifs/End Ifs.


I also need to add a bit that says if the serial number entered is not found on the LostPropertyLog then it is invalid, a tick is neither added or cleared and a message box appears.

Can you help? Thank you!