Choose From Record (otherwise, "get subrecord")

Choose From Record dialog handler:

set subRecord to chooseFromRecord({Person:"KniazidisR", City:"Athens", Phone:"+3 698 00000000", Company:false})

on chooseFromRecord(aRecord as record)
	-- get all existing keys as list
	set oldCliboard to the clipboard
	set the clipboard to aRecord
	set aRecordAsList to the clipboard as list
	set {theKeys, theValues} to {{}, {}}
	repeat with i from 1 to count aRecordAsList by 2
		set end of theKeys to item i of aRecordAsList
		set end of theValues to item (i + 1) of aRecordAsList
	end repeat
	set the clipboard to oldCliboard
	-- select some keys set from all keys
	set newKeys to choose from list theKeys with multiple selections allowed
	if newKeys is false then return
	-- get corresponding values list
	set newValues to {}
	repeat with i from 1 to count theKeys
		set thisKey to item i of theKeys
		if newKeys contains thisKey then set end of newValues to item i of theValues
	end repeat
	-- Create a list containing keys subsequently followed by it's associated value
	set rawList to a reference to {}
	repeat with i from 1 to count newKeys
		tell rawList to set {end, end} to {item i of newKeys, item i of newValues}
	end repeat
	-- Create a record who is similar to records containing only user defined keys in AppleEvents
	set rawRecord to «class seld» of (record {«class usrf»:rawList} as record)
end chooseFromRecord

NOTE: I know, getting sub record without user interacting is simpler. But requires the explicit indicating for key-value pairs. I the sub record to get in the result is big, it will be somewhat problematic:

set sourceRecord to {Person:"KniazidisR", City:"Athens", Phone:"+3 698 00000000", Company:false}
tell sourceRecord to set subRecord to {Person:its Person, Phone:its Phone}