Acrobat User Community Forums

Since you mention spawned pages, then I'm assuming you are working with AcroForms.  A spawned page can be set up to either rename the fields, which is the right way to do it.  All the the fields on a page are renamed in the same way, with a prefix using a dot notation.  All the calculation script needs to do is to determine what the field prefix is for the page, and it can do this by examining it's own name.

For Example:

// split field name on dots.
var aName = event.target.name.split(".");

// remove the original name
aName.pop();

// Build Prefix
var prefix = aName.join(".");

// Do Calculation
event.value = this.getField(prefix + ".QTY") * this.getField(prefix + ".Price");

Of course if you are tolking about dynamic xfa forms the process is very different.