Count the number of Records in a Subgrid

I am hoping someone can shed some light on my problem. I am using the OOTB entity "CASE", I have a customer entity called "SAMPLE". One Case can have many Samples.

On the case form I have a field called "Sample Count". The following code calculates the number of records in the subgrid on the case form and adds the value into the Count Field.

I have this code called "onSave" and "onLoad" of the case form.

However, my issue is the sample count does not seem to calculate onload, It updates instantly when I save the case form. 

In my case this is not sufficient, for example if I create a sample from a case and then save and close the sample...I come back to the case form BUT I need to save before the count is correct.  

function CountNumSamples() {
    if (document.getElementById('Samples')!= null) {
        var count=document.getElementById('Samples').control.get_totalRecordCount();
		var x = parseInt(count);
		Xrm.Page.getAttribute("samplecount").setValue(x);
		Xrm.Page.getAttribute("samplecount").setSubmitMode("always");
		
        }
        else {
            setTimeout("CountNumSamples()", 1000);
        }
    }