Enter additional text into cell containing data

Hi, I was hoping to get some help. I need a macro for excel that will do the following:
1. change the text in the selected cell to black, and then
2. place a line in the cell at the end of the current text (Alt+enter) and then
3. change the text color to red and write UPDATE and insert the date, and then
4. leave the cell selected and open to allow immediate typing.

For example:
In any selected cell
Blah blah blah

After the macro
(BLACK) Blah blah blah
(RED)UPDATE DATE "text"

Then if the macro was used in that cell again it would result in
(BLACK) Blah blah blah
(BLACK)UPDATE DATE (old) "text"
(RED)UPDATE DATE (new) "text"

Thanks for any help that you can provide, this is chewing up a huge amount of my time.

Thanks Barry
I'll try it now and see how it goes.