I'm having difficulty in creating a SOQL query using a custom setting value.
select count (0) from custom_object__c where date_field__c > custom_setting__c.date__c
"Bind variables only allowed in Apex Code"
You can't access a custom setting directly within SOQL. You would need to bind the date to a variable. Something like below should work
Custom_Setting__c cs = Custom_Setting__c.getInstance(); Date myDate = cs.Date_Field__c; List<AggregateResult> result = [select count(Id) total from Custom_Object__c Where Date_Field__c >: myDate];