Summing values using javascript and getting error "Cannot read property 'getValue' of null"

Hello!

I have 7 currency value fields displayed on the opportunity form that I need rolled up into the Potential Rollup currency field. Using the javascript below I'm receiving an error of: "Cannot read property 'getValue' of null". Whether I have a value in one of the fields or not it continues to give me the error and subsequently cannot get a rollup of values in the potential rollup field. 

function CalculateValues() {
var sumRollup=
Xrm.Page.getAttribute("sone_Value1").getValue() +
Xrm.Page.getAttribute("sone_Value2").getValue() +
Xrm.Page.getAttribute("sone_Value3").getValue() +
Xrm.Page.getAttribute("sone_Value4").getValue() +
Xrm.Page.getAttribute("sone_Value5").getValue() +
Xrm.Page.getAttribute("sone_Value6").getValue() +
Xrm.Page.getAttribute("sone_Value7").getValue();
Xrm.Page.getAttribute("sone_PotentialRollup").setValue(sumRollup);
}

I have also tried this script, and it returns the same error.

function CalculateValues() {

   var value1 = Xrm.Page.getAttribute("sone_Value1").getValue();

   var value2 = Xrm.Page.getAttribute("sone_Value2").getValue();

   var value3 = Xrm.Page.getAttribute("sone_Value3").getValue();

   var value4 = Xrm.Page.getAttribute("sone_Value4").getValue();

   var value5 = Xrm.Page.getAttribute("sone_Value5").getValue();

   var value6 = Xrm.Page.getAttribute("sone_Value6").getValue();

   var value7 = Xrm.Page.getAttribute("sone_Value7").getValue();

   var sumRollup = value1 + value2 + value3 + value4 + value5 + value6 + value7;

   // alert(sumRollup);

   Xrm.Page.getAttribute("sone_PotentialRollup").setValue(sumRollup);

}

Any recommendations or insights would be greatly appreciated. 

I was recently solving this using a business rule, but it started creating an incremental loop rather than just summing the values.