populate drop down fields with gform_field_value_?

Hi there,

since a while now, I try to make this example work for me: http://www.gravityhelp.com/documentation/page/Gform_field_value_$parameter_name.
It works for text fields but not for drop down fields. Is there any specific format to be used for drop downs ? I also gave it the string format as shown in here : http://www.gravityhelp.com/documentation/page/Dynamically_Populating_Drop_Down_Fields.
It simply does nothing.
Any help available?

Solved it using the 'gform_pre_render_..'-filter. This one works out of the box!