JavaScript SaveAS from form field help please.

I have read through multiple pages here and used various codes but am having no luck.  The most common error I receive is a cPath unsupported error.  I have place code in the trusted folder script area.  I have tried various button codes but same results.

let me explain my unique situation and what I need to accomplish and maybe there is a simpler way.  all I need is to have a for button simple enough.  it needs when pressed by the user to either silently save as or bring up a dialog, preferably a dialogue that will save the filled pdf as a new name chosen from 2 or three form fields that have been filled out by the user with valid either number or letter characters.  honestly it could even save the form as the same name but to a new folder named from just one form field and i would be able to live with that.

this will be used on only one pc on a closed network and the form will be saved to a local path.  I understand I may still need trusted script which is fine but also that information may not apply since this is only on one pc and all local cant I just have a button script and I am using adobe acrobat pro dc and have the enhanced security settings set to trust the folder??

Any help would be greatly appreciated

something like this for my button script??

this.saveAs("/c/MyDocs/" + getField("Customername")).value;

but this returns unsupported cPath error:

UnsupportedValueError: Value is unsupported. ===> Parameter cPath.

Doc.saveAs:1:AcroForm:Save:Annot1:MouseUp:Action1