LiveCycle Designer uses the same JavaScript engine that Acrobat and Reader does when the LiveCycle form is in the PDF format. So as noted in the Acrobat JavaScript form, the JavaScript engine and capabilities. As explained in the Acrobat JavaScript forum, the JavaScript used in Acrobat or Reader is "sandboxed" or very will isolated from your computer's JavaScript program. This has been done to protect users of Acrobat or Reader form the possibility of running malicious code.
It might be possible if you were to write a add-on plugin using a complied computer program and the information supplied in the Acrobat SDK. Then you would need to manually install this program on your system. For others to use the code you would need to register as a developer with Adobe and have each user install the code to their system at their own risk.