function obrazek(myField, prefix, postfix) {
      var re = new RegExp("^(.*\\S)(\\s*)$");
  myField.focus();
      if (!myField) var myField = window.event      // IE vs ostatni prohlizece
    document.getElementById("obsahla").style.left = myField.clientX + "px";
    document.getElementById("obsahla").style.top = myField.clientY + "px";
  if (document.selection) {
    sel = document.selection.createRange();
            var selection = sel.text;
            var wasEmpty = (selection == "");
            var space = "";
            if (!wasEmpty) {
                  var matches = selection.match(re);
                  if (matches) {
                        selection = RegExp.$1;
                        space = RegExp.$2;
                  }
            }

    sel.text = prefix+selection+postfix+space;
            sel.collapse(false);
            if (wasEmpty) {
                  sel.moveEnd('character',-(prefix.length+1))
            }
            sel.select();
  }

  else {
            if (myField.selectionStart || myField.selectionStart == '0') {
                  var startPos = myField.selectionStart;
                  var endPos = myField.selectionEnd;
                  var selection = myField.value.substring(startPos, endPos);
                  var wasEmpty = (startPos == endPos);
                  var space = "";
                  if (!wasEmpty) {
                        var matches = selection.match(re);
                        if (matches) {
                              selection = RegExp.$1;
                              space = RegExp.$2;
                        }
                  }
                  myField.value = myField.value.substring(0, startPos)
                                                            + prefix+selection+postfix+space
                                                            + myField.value.substring(endPos, myField.value.length);

                  var newPosition;
                  if (wasEmpty) {
                        newPosition = startPos+prefix.length;
                  } else {
                        newPosition = startPos+prefix.length+selection.length+postfix.length+space.length;
                  }
                  myField.setSelectionRange(newPosition, newPosition);
            } else {
                  myField.value += prefix+postfix;
                  myField.setSelectionRange(startPos+prefix.length, startPos+prefix.length);
            }
      }
}