Excel Autofill VBA emulation

This code emulates double click on bottom right  corner of selected cell.

Sub Autofill()
    On Error Resume Next
    Dim checkRange As Range
    
    If RangeState(Selection) = 2 Then: Exit Sub
    
    selMaxRow = Selection.Row + Selection.Rows.Count - 1
    selColsCount = Selection.Columns.Count
    selRowsCount = Selection.Rows.Count
    usedRows = ActiveSheet.UsedRange.Rows.Count
    maxrow = selMaxRow
    row_offset = 0
        
    checkLeft = False
    checkRight = False
    checkCenter = False
    If Selection.Column > 1 Then
        If RangeState(Selection.Offset(0, -1).Resize(selRowsCount, 1)) = 1 Then
            checkLeft = True
        End If
    End If
    If Not checkLeft Then
        If (Selection.Column + selColsCount) < ActiveSheet.Cells.Columns.Count Then
            If RangeState(Selection.Offset(0, selColsCount).Resize(selRowsCount, 1)) = 1 Then: checkRight = True
        End If
    End If

    Set checkRange = Selection.Offset(selRowsCount).Resize(1, selColsCount)
    
    If Not checkLeft And Not checkRight Then
        If RangeState(checkRange) = 1 Then: checkCenter = True
    Else
        checkCenter = True
    End If
    
    For row_offset = 0 To usedRows - Selection.Row - selRowsCount
        If (selMaxRow + row_offset) < usedRows And checkCenter Then
            tmp = RangeState(checkRange.Offset(row_offset))
            If row_offset = 0 Then: center_state = tmp
            If tmp <> center_state Then: checkCenter = False
            If center_state = 3 Then: checkCenter = False
        End If
        
        If checkLeft And center_state = 2 Then
            left_state = RangeState(checkRange.Offset(row_offset, -1).Resize(1, 1))
            If left_state = 2 Or left_state = 3 Then: Exit For
        ElseIf checkRight And center_state = 2 Then
            right_state = RangeState(checkRange.Offset(row_offset, selColsCount).Resize(1, 1))
            If right_state = 2 Or right_state = 3 Then: Exit For
        End If
                
        If checkCenter Then: maxrow = maxrow + 1
    Next
    
    If maxrow > selMaxRow Then
        Selection.Autofill Destination:=Selection.Resize(maxrow - (Selection.Row) + 1)
        Selection.Resize(maxrow - Selection.Row + 1).Select
    End If
End Sub


Function RangeState(rng As Range)
    RangeState = 0
    If IsArray(rng.Formula) Then
        For Each Formula In rng.Formula
            If Formula <> "" Then
                RangeState = RangeState Or 1
            Else
                RangeState = RangeState Or 2
            End If
        Next
    Else
        If rng.Formula <> "" Then
            RangeState = 1
        Else
            RangeState = 2
        End If
    End If
End Function