Hi! someone used "customFormat" in livebindings?

Hi! someone used "customFormat" in livebindings?
i suppose everyday!

I need to access to another field value, just to concat some strings : well, should be easy... but can't make it works as i want :(

i tried in linkcontroltofield , linked to edit.text , writing something like
Owner.OTHERFIELD.Text + " x " + %s
or other syntax as i read in delphi guide ( http://docwiki.embarcadero.com/RADStudio/Seattle/en/Using_Custom_Format_and_Parse_Expressions_in_LiveBindings )
bur result is always "0" or empty string.

same issue in linkLISTcontroltofield using fillexpression property.
i can't read other field value :(

my source is a prototypebindsource , with runtime BindSourceAdapter. can be this source of my problem?

thanks