Append new record inside repeater

Hi,
I have a repeater that initially binded a set of record(let say 20 records). When i click on a button, i will get the next 20 records. So what i want is APPEND the repeater with the next 20 records WITHOUT re-bind the repeater, so the total records will be 40 records.
In the page load i will bind the repeater with a dataset.
Repeater1.DataSource = dsInitial;
Repeater1.DataBind();
When click on a button, i wish to append the new record into the repeater by using dataset. Something like
Repeater1.Row.Append...

Is is possible?
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