In the Math Operators section of the manual take a look at SHIFT and the Btiwise Operators.

The idea is..
From Henrik
To display a "2" you need to set bits 0, 1, 3, 4 and 6 (%01011011 or 91)
You will have to connect the display so that part is on one port and part on another. half and half...
Take the lower 4 bits in the case of #2 (1011) and send them to the display with Port1.
Take the upper 4 bits (0101) and send that to the display with Port2.

Think of Port1 as being 0-3
Port2 as 4-7

Presto... a whole Port...0-7