How to calculate "Future Value" of an investment?

You are not passing the values for the parameters of the function in the function call. It looks like you are also trying to define the function when you are setting the events. value.

I would create a document level script named "FV" and place the following code into script.

function FV(rate, nper, pmt, pv, type) {

  var pow = Math.pow(1 + rate, nper),  fv;

  if (rate) {

   fv = (pmt*(1+rate*type)*(1-pow)/rate)-pv*pow;

  } else {

   fv = -1 * (pv + pmt * nper);

  }

  return fv.toFixed(2);

}

For the field calculation I would use the following code:

var a = Number(this.getField("Q1").value);  // rate;

var b = Number(this.getField("Q1Int").value); // nper;

var c = Number(this.getField("Q1Yr").value); // pmt;

var d = Number(this.getField("Q1Pmt").value); // pv;

var e = 1; // type?

event.value = FV(a, b, c, d, e);

You have not provided any information about the "type" parameter.

From your image I see you have 2 fields with the name "Q2Int" and not one field named "Q1Int". This will generate an error when you try to compute the future value for line one because you have no field named "Q1Int". This error should appear in the Acrobat JavaScript Console if you have it open to set to open upon an error.