Why do I keep getting a verible not defined error in the following code:

Private Sub BtnAdd_Click()
Dim iRow As Long
Dim ws As Worksheet
Dim intMtoprow As Integer
Dim dept As String
Dim x As Integer
Dim y As Integer

Set ws = Worksheets("ProCode")
'find first empty row in database
iRow = ws.Cells(Rows.Count, 1) _
.End(xlUp).Offset(1, 0).Row

'check for the product name
If Trim(Me.CbxProd.Value) = "" Then
Me.CbxProd.SetFocus
MsgBox "Please enter the product name"
Exit Sub
End If

'creates the MSDS#
dept = Me.CboDept.Text
y = 0
intMtoprow = ws.Range("M1000").End(xlUp).Row
For R = 2 To intMtoprow
strCell = ws.Cells(R, 13).Value
If InStr(strCell, dept) = 1 And _
IsNumeric(Mid(strCell, Len(dept) + 1)) Then
x = CInt(Mid(strCell, Len(dept) + 1))
If x y Then
y = x
End If
End If
Next R
'copy the data to the database
Application.EnableEvents = False
ws.Cells(iRow, 2).Value = Me.CbxProd.Value
ws.Cells(iRow, 3).Value = IIf(Me.CkBox1.Value, "Yes", "No")
ws.Cells(iRow, 4).Value = IIf(Me.CkBox2.Value, "Yes", "No")
ws.Cells(iRow, 5).Value = IIf(Me.CkBox3.Value, "Yes", "No")
ws.Cells(iRow, 6).Value = Me.CboFire.Value
ws.Cells(iRow, 7).Value = Me.CboHealth.Value
ws.Cells(iRow, 8).Value = Me.CboReact.Value
ws.Cells(iRow, 9).Value = Me.CboSpec.Value
ws.Cells(iRow, 10).Value = Me.CboDisp.Value
ws.Cells(iRow, 11).Value = Me.TxtQuan.Value
ws.Cells(iRow, 12).Value = Me.TxtDate.Value
ws.Cells(iRow, 13).Value = dept & Format(y + 1, "00#")

Application.EnableEvents = True

'the sort will fire with this line.
ws.Cells(iRow, 1).Value = Me.CbxMfg.Value
FrmProduct.CbxMfg.Value = Me.TxtMan.Value

'clear the data
Me.CbxMfg.Value = ""
Me.CbxProd.Value = ""
Me.CkBox1.Value = False
Me.CkBox2.Value = False
Me.CkBox3.Value = False
Me.CboFire.Value = ""
Me.CboHealth.Value = ""
Me.CboReact.Value = ""
Me.CboSpec.Value = ""
Me.CboDisp.Value = ""
Me.TxtQuan.Value = ""
Me.TxtDate.Value = ""
End Sub