Excel resetting "UsedRange"

Best code that worked for me:

Sub DeleteUnused()
Dim myLastRow As Long
Dim myLastCol As Long
Dim dummyRng As Range
Dim AnyMerged As Variant
'http://www.contextures.on.ca/xlfaqApp.html#Unused
'Helps to reset the usedrange by deleting rows and columns AFTER your true used range

    'Check for merged cells
    AnyMerged = ActiveSheet.UsedRange.MergeCells
    If AnyMerged = True Or IsNull(AnyMerged) Then
        MsgBox "There are merged cells on this sheet." & vbCrLf & _
               "The macro will not work with merged cells.", vbOKOnly + vbCritical, "Macro will be Stopped"
        Exit Sub
    End If

    With ActiveSheet
        myLastRow = 0
        myLastCol = 0
        Set dummyRng = .UsedRange
        On Error Resume Next
        myLastRow = _
        .Cells.Find("*", after:=.Cells(1), _
                    LookIn:=xlFormulas, lookat:=xlWhole, _
                    searchdirection:=xlPrevious, _
                    searchorder:=xlByRows).Row
        myLastCol = _
        .Cells.Find("*", after:=.Cells(1), _
                    LookIn:=xlFormulas, lookat:=xlWhole, _
                    searchdirection:=xlPrevious, _
                    searchorder:=xlByColumns).Column
        On Error GoTo 0

        If myLastRow * myLastCol = 0 Then
            .Columns.Delete
        Else
            .Range(.Cells(myLastRow + 1, 1), _
                   .Cells(.Rows.Count, 1)).EntireRow.Delete
            .Range(.Cells(1, myLastCol + 1), _
                   .Cells(1, .Columns.Count)).EntireColumn.Delete
        End If
    End With

End Sub

I only needed to use Worksheets("Sheet1").UsedRange.Calculate after deleting rows to reset the range.