query error

Sir,

XP/ Vb6/access2003

On the above platform I am trying to run a query in VB6

UPDATE monrepo AS a INNER JOIN (select rocode,sum(ms) as s_ms, sum(hsd) as s_hsd from tr_data where tr_month in ('4') and fy = '2012-2013' group by rocode) AS b ON a.rocode=b.rocode SET a.cur_***_ms = b.s_ms, a.cur_***_hsd = b.s_hsd


I am getting an ambiguous error "Operation must use an updatable query"

Pl. tell me where is the problem and how to get rid off

Neeraj