Custom calculation script - need help

I have 6 fields with property value and 6 related % Ownership, then a grand total field.  My intent is to take property_1 x ownership = value, do the same for the remaining 5 properties, then add all resulting values for a total property value based on % of ownership.  I first entered script below with only one property (without the surrounding ()'s, and it worked fine, then I added the (), copy/pasted the same script & updated the names.  When I inserted the remaining properties, it doesn't work.   (Note, in the example below the calc would be $300,000 X 59% = $177,000).  Where did I mess up on the script?

Thank you so much ~ Michelle

event.value = ( this.getField("MarketValue").value * this.getField("Ownership").value ) + ( this.getField("MarketValue_2").value * this.getField("Ownership_2").value ) + ( this.getField("MarketValue_3").value * this.getField("Ownership_3").value ) + ( this.getField("MarketValue_4").value * this.getField("Ownership_4").value ) + ( this.getField("MarketValue_5").value * this.getField("Ownership_5").value ) + ( this.getField("MarketValue_6").value * this.getField("Ownership_6").value );