Javascript help

Hi all,

So I've got a Boolean field on case that has the same logical name as a field on lead (that field is called new_field). I've connected the case to lead using a lead lookup field called new_lead.

Now whenever I toggle the Boolean field on case I want it to update the related Lead in the Lead lookup field. In the form I've passed the 

I've then written the following Javascript:

function testFunction (executionContext,paramOne){ // paramOne will contain the field logical name (new_field)
    var formContext = executionContext.getFormContext();
    var lead = formContext.getAttribute("new_lead").getValue(); // Get the value of the lead lookup field
    if (lead !== null) { // Check if the lead lookup field contains data
        var leadId = lead[0].id.slice(1, -1); //Slice the lead ID into a usable format
        var paramOneValue = formContext.getAttribute(paramOne).getValue(); // Get the field value of the passed field name
        var entity = {};
        entity.paramOne = paramOneValue; // Trying to update a field in leads that has the same logical name. I'm trying to pass paramOne as a variable
        // Normally paramOne would be the logical name of the field on lead (e.g. new_field). But it doesn't seem to want to use the paramOne pass field name

        var req = new XMLHttpRequest();
        req.open("PATCH", Xrm.Page.context.getClientUrl() + "/api/data/v9.1/leads("+leadId+")", true);
        req.setRequestHeader("OData-MaxVersion", "4.0");
        req.setRequestHeader("OData-Version", "4.0");
        req.setRequestHeader("Accept", "application/json");
        req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
        req.onreadystatechange = function() {
            if (this.readyState === 4) {
                req.onreadystatechange = null;
                if (this.status === 204) {
                    //Success
                } else {
                    Xrm.Utility.alertDialog(this.statusText);
                }
            }
        };
        req.send(JSON.stringify(entity));
    }
}

This seems to give me a error but when I modify the JS to the below it works

function testFunction (executionContext,paramOne){ // paramOne will contain the field logical name (new_field)
    var formContext = executionContext.getFormContext();
    var lead = formContext.getAttribute("new_lead").getValue(); // Get the value of the lead lookup field
    if (lead !== null) { // Check if the lead lookup field contains data
        var leadId = lead[0].id.slice(1, -1); //Slice the lead ID into a usable format
        var paramOneValue = formContext.getAttribute(paramOne).getValue(); // Get the field value of the passed field name
        var entity = {};
        entity.new_field = paramOneValue; // This seems to work if I replace paramOne with the actual lead field logical name

        var req = new XMLHttpRequest();
        req.open("PATCH", Xrm.Page.context.getClientUrl() + "/api/data/v9.1/leads("+leadId+")", true);
        req.setRequestHeader("OData-MaxVersion", "4.0");
        req.setRequestHeader("OData-Version", "4.0");
        req.setRequestHeader("Accept", "application/json");
        req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
        req.onreadystatechange = function() {
            if (this.readyState === 4) {
                req.onreadystatechange = null;
                if (this.status === 204) {
                    //Success
                } else {
                    Xrm.Utility.alertDialog(this.statusText);
                }
            }
        };
        req.send(JSON.stringify(entity));
    }
}

It seems it won't pass the parameter field logical name into my PATCH request.

Is there anyway to dynamically sync this with the passed paramOne?