Below code is wht i'm using to book a serial of 19 digits.

Start: 9904785190112345080
End: 9904785190112345089


The numbers though change due to scientific notation as numbers is
very long.
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Sub UpdateQty()
If IsNumeric(txtStart.Text) And IsNumeric(txtEnd.Text) Then
'txtQty.Text = Format((CDbl(txtStart.Text) - CDbl(txtEnd.Text) -
1), String(Len(txtStart.Text), "0"))
txtQty.Text = (CDbl(txtEnd.Text) - CDbl(txtStart.Text) + 1)
End If
End Sub
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Would appreciate some input.