Count Total amount of related list to update single line record

I am looking for help, i have search most of forums and watched countless videos of custom deluge writing and struggling.

Running a subscription based company which i would like to know how many times my client has attended a class.

I have a custom module (Attendance) which has a look up field connecting it to my deal (Students).

If possible i want to be able to count how many times attendance has been filled out on a single record on the deal

Here is what i currently have but errors come up when i try to Save&Execute

relRecords = zoho.crm.getRelatedRecords('Attendance","Students", input.studentsid.tolong);

count = 0;

for each Attendance Report in gettingrelated

{

count = count + 1;

}

mp = map();

mp.put("rec count",count);

updateResp = zoho.crm.updateRecord("Deals", ClassC,mp);