Issue with VBA and excel code

I have the two following blocks of code to pull data from an external excel sheet:

Sub Host03GetValue()
    p = "c:\Test\"
    'p is the path to the document'
    f = "HOST03.xls"
    'f is the filename of the excel sheet'
    s = "tabvInfo"
    's is the sheet name'
    a = "A16"
    'a is the reference cell'
    Application.ScreenUpdating = False
    For r = 2 To 42
        For c = 1 To 1
            a = Cells(r, c).Address
            Cells(r + 8, c + 1) = GetValue(p, f, s, a)
        Next c
    Next r
    Application.ScreenUpdating = True
End Sub

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Public Function GetValue(path, file, sheet, ref)
'   Retrieves a value from a closed workbook
    Dim arg As String
'   Make sure the file exists
    If Right(path, 1) <> "\" Then path = path & "\"
    If Dir(path & file) = "" Then
        GetValue = "File Not Found"
        Exit Function
    End If
'   Create the argument
    arg = "'" & path & "[" & file & "]" & sheet & "'!" & _
      Range(ref).Range("A1").Address(, , xlR1C1)
'   Execute an XLM macro
    GetValue = ExecuteExcel4Macro(arg)
End Function

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The problem is that for the empty cells, it puts in a o rather than leaving it blank which is my desired effect.  I've tried added in a call for IsEmpty() but unfortunately I'm not able to get it to work properly due to my lack of experience with coding.  Any help/advice is appreciated.