Interest Rate Volatility - An entry is needed here (or enter a Term
  Structure on optional F7 popup input) to turn on the OAS pricing
  feature. Enter as a percent. To see what the numbers look like
  with 0% volatility then enter .0000001 in this field. See next.

Pop-up Input Alternative - Enter volatilty numbers in percent that
  will be in effect for that year. Only enter at the points of
  change. Program will carry input through blank rows.

Options
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Probability that Interest Rates will Increase - Usually 0.5. But
  market participants usually expect that rates have a propensity
  to move in one direction over the other. Use next field to turn
  off after a few years or use F8 to control changing probabilities
  by year.

Years Before Dropping Back to 0.5/0.5 - Time frame before turning
  previous field back to default probability.

Pop-up Input Alternative - Enter probability numbers that will be
  in effect for that year. Numbers must be less that 1. Only enter
  at the points of change. Program will carry input through blank
  rows. Last number entered should be .5 to return probability back
  to neutral.

Effective Duration Deltas - When measuring a bond's effective
  duration BondCalc shifts the benchmark yield curve by a nominal
  amount. Using new forward spot rates, and holding volatility and
  the bond's OAS constant, a new bond price is solved for. Using
  this, the OAS Duration and other measures of a bond's price
  sensitivity to changes in interest rates can be calculated.

Also Calculate when No Calls Present - By default BondCalc does not
  expend the overhead to calculate OAS when there are no calls
  present, except when backsolving with OAS. Entering a 1 here
  will allow testing to see that there is no option value when
  there are no calls. This flag will also turn on OAS for bonds
  with greater than 30 years to maturity, as they take a long time
  to calculate.

Opt Key Years for Partial Durations - If these are blank the
  partial durations will be broken into the benchmark years on the
  used yield curve. These override. A 0.5 year one will always be
  included.