Scripting error with daysoverdue

Hi guys & girls,

we have a script that sends emails to our overdue customers however I was hoping to edit this so that it can send to all customers providing that they are over a specific balance (balancethreshold).  I have the following search parameters as part of my script:

var customerFilters = [ new nlobjSearchFilter('daysoverdue',null,'greaterthanorequalto',daysoverduemin),new nlobjSearchFilter('daysoverdue',null,'lessthanorequalto',daysoverduemax),new nlobjSearchFilter('overduebalance',null,'greaterthan',balancethreshold) ];

However even when i use 0 for my daysoverduemin the only emails sent are to customers that are at least 1 day overdue? I even tried using a negative number just in case but that also did not work.  Any suggestions would be much appreciated.