Creating a loop with an IF variable -- Run-time error '1004' - excel

Question

I'm trying to create a loop based on data in Column L. Data in Column L is formatted as Text and contains dates. If a match is found, the entire Row has to be highlighted in yellow.
Sub Forn()
Dim ws As Worksheet
Set ws = ThisWorkbook.Worksheets(1)
Dim strSearchText As String
strSearchText = Format(DateAdd("m", 2, Now()), "yyyymm")
Dim rngSearchArea As Range
Set rngSearchArea = ws.Range(Range("L10"), ws.Range("L" & ws.Range("L:L").Cells.Count).End(xlUp))
Dim strFirstFound As String
Dim rngCurrentFound As Range
Set rngCurrentFound = ws.Range("L10")
Set rngCurrentFound = rngSearchArea.Find(What:=strSearchText, After:=rngCurrentFound, LookIn:=xlFormulas, _
LookAt:=xlPart, SearchOrder:=xlByColumns, SearchDirection:=xlNext, _
MatchCase:=True, SearchFormat:=False)
If rngCurrentFound Is Nothing Then
MsgBox "INGEN TREFF"
Exit Sub
End If
rngCurrentFound.Resize(1, 16).Offset(0, -11).Interior.ColorIndex = 6
strFirstFound = rngCurrentFound.Address
Dim rngSource As Range
Dim rngNextFound As Range
Do
Set rngNextFound = rngSearchArea.FindNext(rngCurrentFound)
If rngNextFound.Row > rngCurrentFound.Row Then
rngCurrentFound.Resize(1, 16).Offset(0, -11).Interior.ColorIndex = 6
Else
Set rngSource = ws.Range(rngCurrentFound, ws.UsedRange.Cells(ws.UsedRange.Cells.Count))
End If
Set rngCurrentFound = rngSearchArea.FindNext(rngCurrentFound)
Loop While rngCurrentFound.Address <> strFirstFound
End Sub
I'm getting Run-time error '1004':
Method 'Range' of object '_Worksheet' failed.
This exact same code worked for me yesterday and I'm at a complete loss as to what needs to be changed here.
UPD: the error is caused by launching the Macro from PERSONAL.XLSB --
Set ws = ThisWorkbook.Worksheets(1)
no longer works as needed.

Answer 1

Using ThisWorkbook in a macro tells VBA that you want to access the workbook where the code is stored. If you move your code to the Personal.xlsb, it will access Personal.xlsb and it's sheets - and that's probably not what you want.
You put a macro in the Personal usually to have it available all the time, e.g. via a Keyboard shortcut.
If you want the code to work on the currently visible workbook, replace ThisWorkbook simply by ActiveWorkbook - but you need to ensure that it makes sense to run the macro on that workbook.
If you want to execute it always on the same workbook, it makes no sense to have it in the personal - just keep it in the workbook itself.
If you want to select the workbook first, add a fileopen-dialog to your code, open the workbook using Workbooks.Open and use the workbook-reference returned by the open-command.