You will make text field with tag [DAY_WEEK], it will return number of the day in week (1-7)
Then check the tick to activate bitmap font (I think link to the bitmap font tutorial was in your other thread).
Then assign prepared image of the whole strip of letters (this you have to make in graphic tool like photoshop, gimp or even MS powerpoint is good option for such simple images) to according letter.
Something like this for each digit from 1 to 7:
