delphi - DBGrid: how to prevent a row from being selected? -

i have grid of entries user click on multi-select process. of entries invalid based upon values of first selected row.

i know dbgrid.selectedrows.currentrowselected, cannot find suitable place checking conditions set true or false.

something this:

var   bm: tbookmark;   cachedidentity: string;   canselect: boolean; begin   dgbskypeconversations   begin     if selectedrows.count > 0     begin       datasource.dataset.disablecontrols;       bm := datasource.dataset.getbookmark;       cachedidentity := datasource.dataset.fieldbyname('identity').asstring;       datasource.dataset.gotobookmark(selectedrows[0]);       canselect := datasource.dataset.fieldbyname('identity').asstring <> cachedidentity;       datasource.dataset.gotobookmark(bm);       datasource.dataset.freebookmark(bm);       selectedrows.currentrowselected := canselect;        datasource.dataset.enablecontrols;     end;   end end; 

i have tried onmousedown events in application.onmessage , of dbgrid , form, not work, , there no tbookmarklist.beforeinsertitem event. can or must change?

i not make complicated.
if comparison takes place on first selection.
code use here has hardcoded value.
no jump around bookmarks.

// first selection-----------------------------  if dbgrid1.selectedrows.count = 1 begin    cachedidentity := 'sonnenbrille'; // sunglasses  //cachedidentity := datasource.dataset.fieldbyname('identity').asstring;    exit; end; 

do comparison

if dbgrid1.selectedrows.currentrowselected begin  //if cachedidentity <> datasource.dataset.fieldbyname('identity').asstring    if pos(lookingfor,dbgrid1.datasource.dataset.fieldbyname('haupttxt').asstring)=0     dbgrid1.selectedrows.currentrowselected := false;    showmessage(inttostr(dbgrid1.selectedrows.count)); end; 

we can see 2 selected so
showmessage(inttostr(dbgrid1.selectedrows.count));

shows 2

now want select line

sportlich, elegante gucci sonnenbrille

we know simple pos() sonnenbrille find sonnenbrille pos() = 0, selection-will not take place.

showmessage(inttostr(dbgrid1.selectedrows.count));

shows 2 too

code:

var cachedidentity : string;  procedure tform2.canselectedv1; begin     // first selection-----------------------------  if dbgrid1.selectedrows.count = 1 begin    cachedidentity := 'sonnenbrille'; // sunglasses  //cachedidentity := datasource.dataset.fieldbyname('identity').asstring;    exit; end; if dbgrid1.selectedrows.currentrowselected  begin  //if cachedidentity <> datasource.dataset.fieldbyname('identity').asstring    if pos(lookingfor,dbgrid1.datasource.dataset.fieldbyname('haupttxt').asstring)=0     dbgrid1.selectedrows.currentrowselected := false;    showmessage(inttostr(dbgrid1.selectedrows.count));  end; end;  procedure tform2.dbgrid1mouseup(sender: tobject; button: tmousebutton;   shift: tshiftstate; x, y: integer); begin canselectedv1; end;  procedure tform2.dbgrid1keyup(sender: tobject; var key: word;   shift: tshiftstate); begin canselectedv1; end;  end.