Adjusted total based on importance of ranking score

Hi there,

I'm currently putting together an evaulation form to grade User Interface designs. I need some help creating a formula and it's not really something I'm familiar with.

I have several criteria that I am ranking out of 5 as well as an "importance" score depending on how important the particular criteria is to the user interface.

Eg:

Reading characters on the screen is easy - Score: 4 out of 5 - Importance: 5 out of 5
Uses Highlighting to help simplify task - Score: 1 out of 5 - Importance: 2 out of 5
Organisation of information is clear - Score: 5 out of 5 - Importance: 5 out of 5
Sequence/flow of screens is clear - Score: 3 out of 5 - Importance: 4 out of 5

For example 'Uses Highlighting to help simplify task' scores poorly (1 out of 5), however it's not really that important to the user interface (2 out of 5).

So what I need is a formula that can give me an adjusted percentage for the Score and Importance. The Importance score is like a Weighting (is that the right term?) to show a true percentage that can be compared with other user interface evaluations.

Hopefully this makes sense....any help or advice would be much appreciated!