Erreur d'exécution '13' : Incompatibilité de type

Dim cel As Range
Set cel = c.Find(cel.Value, After:=cel, LookIn:=xlFormulas, _
LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, _
MatchCase:=False, SearchFormat:=False)

            Set Plage = Range(NI1hdr.Offset(1, 0), NI1hdr.Offset(lastcel.Row, 0))
            Set C = Plage.Find(cel.Value, After:=cel, LookIn:=xlFormulas, _
                LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, _
                MatchCase:=False, SearchFormat:=False)
            Do
                If C Is Nothing Then Exit Do
                isinarray = False
                For k = 1 To j
                    If packhdr.Offset(C.Row - firstrow + 1, 0).Value = pack(k) Then isinarray = True 'check if packhdr.value is in NI1(i, j)
                Next k
                If Not isinarray Then
                    j = j + 1
                    ReDim Preserve pack(0 To j)
                    pack(j) = packhdr.Offset(C.Row - firstrow + 1, 0).Value
                End If
                Set C = Plage.FindNext(C) 'find next row with the current NI1
            Loop While C.Row <> firstfindrow

Dim Plage as range, C as range

Sub Macro1()

'Dim i As ...
'Dim NI1hdr As Range
'Dim lastcel As Range
'Dim NI1() As ...
'Dim NI1tmp() As ...
'Dim j As ...
'Dim MaxNbPack As ...
'Dim cel As Range
'Dim isinarray As Boolean
'Dim pack() As ...
'Dim fistfindrow As Integer
'Dim c As Range
'Dim packhdr As Range
'Dim packtmp() As ...
'Dim nbNI1 As ...

'Set NI1hdr = ...
'Set lastcel = ...
'Set packhdr - ...

' we are at the start. we make a list of all NI1.
i = 1
Do While NI1hdr.Offset(i, 0).Value = vbNullString 'loop until we find a non-empty cell (should be quick)
    i = i + 1
    If i = lastcel.Row Then MsgBox "No non-empty cells in the NI1 column: exiting macro now.": Exit Sub
Loop
ReDim Preserve NI1(0 To 0)
ReDim Preserve NI1tmp(0 To 0)
i = 0
MaxNbPack = 0
For Each cel In Range("I" & NI1hdr.Row + 1, "I" & lastcel.Row)
    If cel Is Nothing Then Resume Next
    isinarray = False
    For k = LBound(NI1tmp) To UBound(NI1tmp)
        If NI1tmp(k) = cel.Value Then isinarray = True 'check if NI1 is in the tmp array which mirrors the real one
    Next k
    j = 0
    If (Not isinarray) And cel.Value <> "" Then 'copy the NI1 to the array in i-th position
        'fill the pack array, then later assign it to the NI1 array
        ReDim Preserve pack(0 To j)
        pack(0) = cel.Value
        j = j + 1
        ReDim Preserve pack(0 To j)
        pack(j) = packhdr.Offset(cel.Row - firstrow + 1, 0).Value 'put the first found value into the first box
        firstfindrow = cel.Row
        Set c = Range(NI1hdr.Offset(1, 0), NI1hdr.Offset(lastcel.Row, 0))
        Set cel = c.Find(cel.Value, LookIn:=xlFormulas, _
           LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, _
            MatchCase:=False, SearchFormat:=False)
        Do
            If cel Is Nothing Then Exit Do
            isinarray = False
            For k = 1 To j
                If packhdr.Offset(cel.Row - firstrow + 1, 0).Value = pack(k) Then isinarray = True 'check if packhdr.value is in NI1(i, j)
            Next k
            If Not isinarray Then
                j = j + 1
                ReDim Preserve pack(0 To j)
                pack(j) = packhdr.Offset(cel.Row - firstrow + 1, 0).Value
            End If
            Set cel = c.FindNext(cel) 'find next row with the current NI1
        Loop While cel.Row <> firstfindrow
        If j > MaxNbPack Then MaxNbPack = j
        ReDim Preserve packtmp(0 To i)
        packtmp(i) = j
        ReDim Preserve NI1(0 To i)
        NI1(i) = pack
        ReDim Preserve NI1tmp(0 To i)
        NI1tmp(i) = NI1(i)(0)
        i = i + 1
    End If
Next cel
nbNI1 = i - 1
End Sub