Type mismatch error on startup

[dmwa]

Im doing a little data logging, A1 is an external reference and takes a few seconds to connect. once connected and it reads the variable numerical value and the script runs fine and logs every change of value in A1. problem is when first opening the workbook the script goes into a type mismatch error because the value of A1 as not updated yet and reads #N/A. I tried using a check box to run the script but it only logs the first change and seems to not log any further changes. any help would be greatly appreciated

Private Sub Worksheet_Calculate()
Static oldval
If Range("A1").Value <> oldval Then
    oldval = Range("A1").Value
    Range("A3").EntireRow.Insert
    Range("A1:C1").Select
    Selection.Copy
    Range("A3").Select
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
   Application.CutCopyMode = False
   Range("A31").EntireRow.Delete
  
End If
End Sub

[JKwan]

check to see if value is #n/a first

    If Application.IsNA(Range("A1")) Then
        MsgBox "error"
    End If

[SamT]

Private Sub Worksheet_Change(ByVal Target As Range)

If Target.Address <> "$A$1" Then Exit Sub

   Rows(3).Insert
   Range("A1:C1").Copy Range("A3:C3")
   Application.CutCopyMode = False
   
   Rows(31).Delete

End Sub

[dmwa]

Private Sub Worksheet_Change(ByVal Target As Range)

If Target.Address <> "$A$1" Then Exit Sub

   Rows(3).Insert
   Range("A1:C1").Copy Range("A3:C3")
   Application.CutCopyMode = False
   
   Rows(31).Delete

End Sub

[SamT]

???

[dmwa]

Thank you!!