normal convention is to use comma's tather than semi colons tho' there are some language variations, which might apply to you.
And dates need to be supplied in US format of mm/dd/yyyy
so try
Script : TARIH_Q: DSum("DOVIZ_BORC","CH_HAREKET","TARIH>#" & format([TARIH],"mm/dd/yyyy") & "#")
you may also need to protect [TARIH] against nulls