Work Flow values

Hello All,

I was wondering.  can you assign multiple values to a WF?  Like this:

JoinFieldValue('<Account>', [<AccountId>], '<PrimaryBillToCountry>') = 'USA' or "Canada"

or do I have to write it as:

JoinFieldValue('<Account>', [<AccountId>], '<PrimaryBillToCountry>') = 'USA'

or

JoinFieldValue('<Account>', [<AccountId>], '<PrimaryBillToCountry>') = "Canada"

If I can perform the first.  Is there a limit to the vlaues that I can use?

JoinFieldValue('<Account>', [<AccountId>], '<PrimaryBillToCountry>') = 'USA' or "Canada" or "Africa" or China".....

Cheers