Need help creating custom links in reports. Anybody have a general form I could use?

I've set up a custom button to clone account records (don't ask - it's a long story).  Everything checks out ok but I can't get a multi-select field to pass through to the new record.  I've tried everything.  Here's what I am using.  The bold red line is the one that isn't working.

https://na2.salesforce.com/001/e?
acc2={!Account.Name}&
00N30000000lVLT_selected={!Account.Ranking__c}&
00N30000000lsJD={!Account.Fortune_Rank__c}&
acc12={!Account.Website}&
acc17street={!Account.BillingStreet}&
acc17city={!Account.BillingCity}&
acc17state={!Account.BillingState}&
acc17zip={!Account.BillingPostalCode}&
acc17country={!Account.BillingCountry}&
acc7={!Account.Industry}&
acc15={!Account.NumberOfEmployees}&
00N40000001LlGl={!Account.of_Employees__c}

Thanks.

Lee