Workflow automation between two modules

Hi,

we would like to know if workflow rules can allow us to automaticaly change the value within a multiselect custom field if the status of another field in another module change too.

Here is the case:

We have in Contacts Module a custom field named "Qualification" filled with various values from a multiselect list.

Those Contacts are generally linked to Deals in order to have revelant contact information for each of our deals.

We would like to change contact qualification from whatsoever it is to "Client" when a deal is won.

Seems pretty simple but, this feature is not available within our Standard plan.

We would like to know if it can be accomplished with a superior plan before switching to it.

Thanks in advance for replying.