Making a bracha for someone else, can then use for one's self?
Reuvan is unable to make kiddush and has asked Shimon (who already made kiddush for himself) to make kiddush for him (Reuvan). Shimon, however, says he can't drink the wine. Reuvan therefore is hearing Kiddush from Shimon then drink the wine. After this is done, Shimon decides that he does want to have some wine as well. May Shimon drink without a bracha and rely on the bracha he had originally made for Reuvan in order to be motzei him in Kiddush (assuming he hasn't interrupted with speaking, etc.)? The question is, since he had only Reuvan and not himself in mind, would the bracha help for his own drinking?
Similarly the same question could be asked in regards to other brachos (that are made on a mitzvah.) For example putting on tallis or tefillin, hanging a mezuzah, etc. (all assuming there is no hefsek in the middle, etc.). If Reuvan couldn't make the bracha himself but Shimon could and did in fact make the bracha on the mitzvah but had in mind that it should only be done for Reuvan, can he then do the mitzvah and rely on that bracha?
Seemingly, it does not work.
The Mishna Berura there extends the case to even where you did not explicitly have intention to drink other wine, you just had "stam da'as." But when you had specific intention to not drink wine, it would not work. Intention to have some of what you are making the blessing on, either explicit or implicit, is necessary.
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