Any keyframe data from AE can be copied and pasted as text into a text editor. Equally, if the text is formatted correctly, any text from the text editor can then be pasted back into the keyframe layer that it came from. So you could use this method to create some keyframes on a slider control, paste them into TextEdit, then continue the formatting of the text as shown in the text file using your own data. Bear in mind you may have to tweak your data to fit a range that makes sense on screen – either beforehand in another application, or after using Expressions. Hope this helps.