Double Barrier options are path-dependent options. They have two pre-defined barriers, one higher and one lower than the current asset price. If the asset price crosses either barrier, the option is either initiated (for an in or knock-in barrier) or terminates (if an out or knock-out barrier).
Double Barrier options are targeted at investors who expect the value of an asset to vary within a range. They are commonly used in forex and commodities markets, and tend to be cheaper than their vanilla counterparts.
This Excel spreadsheet implements the numerical algorithm proposed by Ikeda and Kunitomo in “Pricing options with curved boundaries, Mathematical Finance, 2 (1992): 275-298)”. It is only valid if the strike price is between the upper and lower barrier.