S Control Help .... Map Nearby Accounts

We've downloaded the Map Nearby Accounts app from AppExchange, but we same to have discovered a small glitch if we have the zip+4 zip codes in the Account record. I want to just strip out the first 5 digits.

This is what I came up with, but it doesn't seem to work.

var zip= "{! LEFT( "!Account.BillingPostalCode" , 5) }";