PowerBuilder - select multiple rows on datawindow

On Datawindow clicked event -

if row>0 then
    if keydown(keycontrol!) then
        this.selectrow(row,true) 
        Else
            this.selectrow(0,false)
            this.selectrow(row,true)
    end if 
    if keydown(keyshift!) then
        this.event trigger ue_shift(row)
    end if
end if
li_selectedrow=row
this.setrow(row) 

Custom event code ue_shift

long ll_oldrow,ll_newrow,ll_counter,ll_startrow,ll_endrow
ll_oldrow=li_selectedrow 

if ll_oldrow>al_row then
    ll_startrow=al_row
    ll_endrow=ll_oldrow
else
    ll_startrow=ll_oldrow
    ll_endrow=al_row
end if

for ll_counter=ll_startrow to ll_endrow step 1
    this.selectrow(ll_counter,true)
Next

this.setrow(al_row)
this.setcolumn(1)


return 0

Thank you!!