Populate a PDF done with Adobe Livecycle Designer

I have a pdf from an institution and I have been asked to populate it directly with data saved in an excel file. I have found that the pdf was done with adobe livecycle designer and with that program I can see the name of the fields in the form.

The pdf can be found in:

https://sedeelectronica.bde.es/f/websede/content/SPA/Form_TRA_clientes .pdf

I have thought to use a VB macro in the excel file to populate the pdf. I have been searching on Internet but by now, I am only able to read the values of the fields, but I can't change them.

Here is the main code:

Set gApp = CreateObject("AcroExch.app")
Set avDoc = CreateObject("AcroExch.AVDoc")
If avDoc.Open(FileNm, "") Then
   Set pdDoc = avDoc.GetPDDoc()
   Set jso = pdDoc.GetJSObject()
  jso.Getfield("FrmSolicitudTransferenciaEuros[0].FormContent[0].ordena nte[0].datosOrdenanteExterno[0].ordenante[0]").Value  = "new value"

    pdDoc.Save 1, FileNm
    pdDoc.Close
End If

avDoc.Close (True)

When I open the pdf, the "new value" doesn't appear in the field and if I debug it, jso.Getfield("FrmSolicitudTransferenciaEuros[0].FormContent[0].ordenan te[0].datosOrdenanteExterno[0].ordenante[0]").Value has always the same value, it doesn't change.

I have tried with several fields with the same results.

Any ideas?

Thank you in advance.