Implementing "at" and "for" clause of COGNOS in WEBI 3.1

Hi,

I am trying to convert few COGNOS report into WEBI reports. In cognos reports some objects are getting aggregated by at and for clause e.g,

"XSUM(XSUM(XMAX(REPORT_DOC_USAGE.TOTAL_PRINTED  for REPORT_DOC_USAGE.SESSION_KEY,REPORT_DOC_USAGE.DOC_KEY )  at REPORT_DOC_USAGE.DOC_KEY,REPORT_DOC_USAGE.DOCUMENT_NAME,REPORT_DOC_USAGE.SESSION_KEY  for REPORT_DOC_USAGE.DOC_KEY,REPORT_DOC_USAGE.DOCUMENT_NAME )  at REPORT_DOC_USAGE.DOC_KEY,REPORT_DOC_USAGE.DOCUMENT_NAME )  as  Total_Printed11,"

I am trying to implement this in webi. Please let me know how to do that.