What version of Symposium do you have?
RFWhites solution would only work with version 5.0 and above as it uses the wild call variable not available any earlier.
One other option would be to use an intrinsic to generate your call distribution. Choose one that changes on a regular basis. You could combine two or three to increase the amount it moves.
1) At the top of the script assign the intrinsic(s) to a call variable e.g. calls answered in last ten minutes
ASSIGN ANSWERED CALL COUNT skillset TO cv_splitter
2) This will give you a call variable, cv_splitter, that changes on a regular basis. Dependent upon call volumes you could use one busy skillset or two or three in a list (need to create a variable for this)
3) Then create a WHERE statement that distributes the call
WHERE cv_splitter EQUALS
VALUE 0,4,8,12 : EXECUTE SCRIPT_A
VALUE 1,2,3,5,6,7,9,10,11 : EXECUTE SCRIPT_B
DEFAULT : EXECUTE SCRIPT_B
END WHERE
The numbers you need to use will depend upon the intrinsic you use and its likely range i.e. in my call centre, we never get more than 12 calls in any 10 minute period!
I would suggest putting the splitter bit in the master in its own section. Do a CDN look-up in the master to send only the appropriate calls to this section.
The 'treatments' are execute script_A or _B. You would put what you want to do in those scripts.
This will allow you to see how many calls are hitting each application and allow you to tweak it accordingly so on average you achieve the desired split.