function replacestr(const s, srch, replace: string): string;
var
i : integer;
source: string;
begin
source:= s;
result:= '';
repeat
i:=pos(srch, source);
if i > 0 then begin
result := result + copy(source,1,i-1) + replace;
source := copy (source,i+length(srch),maxint);
end
else
result := result + source;
until i<=0;
end;