Function to check the sheet name exist or not based on sheet values

Hi,

I need to check when one of the values in the column is equal to a worksheet that is currently in the excel file. Just a message box that says something like “A worksheet currently exists with the name of a value in this list. Please rename the current worksheet”. When the user gets the message box, they should be able to click “OK” and the function ends.
Is it possible to modify this code?

Option Explicit
Option Compare Text
Sub sheets_from_colvalues(control As IRibbonControl)
 
'Const sh1 As String = "Sheet1"
Dim sh1 As String
sh1 = ActiveSheet.Name

Dim a As Variant, x As Worksheet, sh As Worksheet
Dim rws&, cls&, p&, i&, rr&, b As Boolean
Dim cl&

cl = Selection.Column
Application.ScreenUpdating = False
Sheets(sh1).Activate

rws = Cells.Find("*", , , , xlByRows, xlPrevious).Row
cls = Cells.Find("*", , , , xlByColumns, xlPrevious).Column

Set x = Sheets.Add(After:=Sheets(sh1))
Sheets(sh1).Cells(1).Resize(rws, cls).Copy x.Cells(1)
Set a = x.Cells(1).Resize(rws, cls)
a.Sort a(1, cl), 2, Header:=xlYes
a = a.Resize(rws + 1)
    p = 2
    
    For i = p To rws + 1
        If a(i, cl) <> a(p, cl) Then
            b = False
            
            For Each sh In Worksheets
                If sh.Name = a(p, cl) Then b = True: Exit For
            Next
            If Not b Then
               
                With Sheets.Add
                  
                   .Name = a(p, cl)
                    x.Cells(1).Resize(, cls).Copy .Cells(1)
                    rr = .Cells.Find("*", , , , xlByRows, xlPrevious).Row + 1
                    x.Cells(p, 1).Resize(i - p, cls).Cut .Cells(rr, 1)
                    .Columns.AutoFit
                End With
            End If
            p = i
        End If
    Next i
Application.DisplayAlerts = False
    x.Delete
Application.DisplayAlerts = True
Sheets(sh1).Activate
Application.ScreenUpdating = True
End Sub

Thanks in advance!

can you attach a sample file ?
you can use this code

Sub M_snb()
    MsgBox shexist("sheet1b")
End Sub
 
Function shexist(c00)
    shexist = Evaluate("isref(" & c00 & "!A1)")
End Function

try this code

Option Compare Text
Sub sheets_from_colvalues()
 
Lr = Cells(Rows.Count, "A").End(xlUp).Row
For r = 2 To Lr
  shname = Cells(r, 1)
  If shexist(shname) Then
    Sheets(shname).Select
    MsgBox "A worksheet currently exists with the name of a value in this list. Please rename the current worksheet"
    Exit For
  End If
Next
End Sub
 
Function shexist(c00)
    shexist = Evaluate("isref(" & c00 & "!A1)")
End Function

I can not understand your code