What is the script for addition in PDF Custom Calculation Script

Hello, I am pretty new to scripting.  Can someone please let me know what the script is for adding fields?  I have this formula right now, but it is only adding the first one. If I put a + in place of the , then nothing happens.  Can someone please let me know what I am doing wrong?  The totals are based off of TaxDue1 + TaxDue2, etc.

event.value=this.getField("TaxDue1").value,this.getField("TaxDue2").value,("TaxDue3").value,("TaxDue4").value,("TaxDue5").value,("TaxDue6").value,("TaxDue7").value,("TaxDue8").value,("TaxDue9").value,("TaxDue10").value;if(event.value==0)event.value="";