I created both a multi-select picklist and a formula field to pull values from the multi-select picklist. 

My formula is: IF(ISNULL( Software_Version__C),  0 ,  Software_Version__C)

However, I get an error saying: "Error" Software_Version__c is a multi-select picklist field.  Multi-select picklist fields are only supported in certain functions" with a link to the functions which show:

Multi-select picklist fields can only be used in the following functions:

• INCLUDES
• ISBLANK
• ISNULL
• ISCHANGED (Only in assignment rules, validation rules, workflow field updates, and workflow rules in which the trigger type is set to Every time a record is created or edited)
• PRIORVALUE (Only in assignment rules, validation rules, workflow field updates, and workflow rules in which the trigger type is set to Every time a record is created or edited)

Any suggestions???