Okkk..Using text.buf.to.field would not work because that refers to a Multiline text Form field so its not really applicable to this case.
You could try the below command, text.write
function long text.write (string text_field, string lang, string kw1, string kw2, string kw3, string kw4, string tgroup, string edit_opt, string tmp_file [, long bidi] [, string rtf_file])
This adds a new text to the text manager and assigns a new text number to the text.
string text_field The name of the new text field. See Text fields overview. This returns the text number for the new field.
string lang This specifies the language for the new text.
string kw1 Use these arguments to specify key words for the text.
string tgroup This specifies the name of the text group to which the text must be assigned. If you specify an empty string here, the text is assigned to the user's default group.
string edit_opt This specifies the type of window in which the text must be displayed.
string tmp_file The name of the file where the text for the new field is stored. The contents of this file is changed before the text is stored, Long lines are wrapped to meet the line width of the text group to which the text is assigned.
[long bidi] Use this optional argument to indicate the text alignment. Possible values are:
true text is right justified
false text is left justified; this is the default option
[string rtf_file] The name of the file in which the RTF version of the text must be stored. This is an optional argument. The usage of this argument depends on the settings of the text group as defined in the tgroup argument. If this is an empty string, no text is retrieved and the function returns 0.
>0 success; returns the number of lines written
Here you can mention the language specifically as well.. The Only challenge is that you need to create a file with the contents of the different language. Otherwise it looks pretty straightforward..