Excel VBA Runtime Error 1004 when renaming ActiveSheet - vba

Question

I'm at a loss when trying to figure out where this code is tripping up. I am looking to rename the activesheet by using a concat of two ranges on the activesheet and some static text. When only one worksheet is in the workbook, the code works great. As soon as a second worksheet is added, I get a Runtime Error 1004. I'll highlight the line of code where it is breaking. This code currently resides in a normal module.
Option Explicit
Sub updateName()
Dim fNumber
Dim pCheckNumber
Dim asName As String
Dim tempASName As String
Dim worksheetName As Object
If ActiveSheet.Name = "Launch Page" Then Exit Sub
fNumber = ActiveSheet.Range("FlightNumber").Value
pCheckNumber = ActiveSheet.Range("PerformanceCheckNumber").Value
If fNumber <> "" And pCheckNumber <> "" Then
tempASName = "Flight " & fNumber & " | Run " & pCheckNumber & " (0.0%)"
asName = tempASName
MsgBox ActiveSheet.Name & vbCr & asName
ActiveSheet.Name = asName
worksheetName.Caption = asName
Else
Exit Sub
End If
End Sub
I'm in the process of adding error checking to ensure that I don't have duplicate sheet names. However, due to the nature of the field names, this will never occur.
I appreciate all of the insights!

Answer 1

The error you are reporting is, most likely, provoked because of trying to rename a Worksheet by using a name already in use. Here you have a small code to avoid this kind of situations:
Dim newName As String: newName = "sheet1"
Dim addition As String: addition = "_2"
Do While (Not sheetNameFree(newName))
newName = newName & addition
Loop
Where sheetNameFree is defined by:
Function sheetNameFree(curName As String) As Boolean
sheetNameFree = True
For Each Sheet In ActiveWorkbook.Sheets
If (LCase(Sheet.Name) = LCase(curName)) Then
sheetNameFree = False
Exit Function
End If
Next Sheet
End Function
You can adapt this code to your specific needs (for example, by converting addition into a number which grows after each wrong name).
In your code I see one other problem (although it shouldn't be triggering a 1004 error): you are accessing the property Caption from an non-instantiated object (worksheetName), whose exact functionality is not too clear. Just delete this line.
NOTE: good point from KazJaw, you might be using an illegal character. If fNumber and pCheckNumber are numbers or letters, it would be OK.
NOTE2: if with worksheetName you want to refer to an ActiveX Label in your workSheet, better do: ActiveSheet.Label1.Caption (where Label1 is the name of the Label). You cannot define worksheetName as a Label, because it is not a "conventional Label".