The code to open a report also takes a WHERE parameter, set this to equal the current record on your form. This would look something like-
DoCmd.OpenReport "rptName", acViewPreview, wherecondition:="[uniquefield] = " & Forms!frmName!uniquefield
or, if your primary key is a string-
DoCmd.OpenReport "rptName", acViewPreview, wherecondition:="[uniquefield] = '" & Forms!frmName!uniquefield & "'"
Replace the various bits with as appropriate.