How to ignore blank cells in a find macro

Hello, this is what i have so far. But if either of the search values from MyArr (A1 or A2) are left blank then it will search for a blank cell. How do I prevent this? Help much appreciated.

Option Explicit
Sub Mark_Cells_In_Column()
 Dim FirstAddress As String, I As Long
 Dim MyArr As Variant, Rng As Range, Sh As Worksheet

 Sheets("Sheet1").Select
 With Application
    .ScreenUpdating = False
    .EnableEvents = False
 End With
 MyArr = Array(Range("A1").Value, Range("A2").Value)
 For Each Sh In ThisWorkbook.Worksheets
    If Sh.Name <> "Sheet1" Then
        With Sh.Range("A:A")
            .Offset(0, 1).ClearContents
            For I = LBound(MyArr) To UBound(MyArr)
                Set Rng = .Find(What:=MyArr(I), After:=.Cells(.Cells.Count), _
                    LookIn:=xlFormulas, LookAt:=xlWhole, SearchOrder:=xlByRows, _
                    SearchDirection:=xlNext, MatchCase:=False)
                If Not Rng Is Nothing Then
                    FirstAddress = Rng.Address
                    Do
                        Rng.Offset(0, 1).Value = Range("B1").Value  'B1<=|'
                        Rng.Offset(0, 2).Value = Range("C1").Value  'C1<=|'
                        Set Rng = .FindNext(Rng)
                    Loop While Not Rng Is Nothing And Rng.Address <> FirstAddress
                End If
            Next I
        End With
    End If
 Next Sh
 With Application
    .ScreenUpdating = True
    .EnableEvents = True
 End With
End Sub