Repeated Vignère Cipher
Do you mean that if you have a key of length $l$ say $k_1, ..., k_l$, and a plain $m_1, ..., m_n$, that you want to do $c_i = m_i + \sum_{j=1}^l k_j$ ? (Each plain letter is added with each key letter)

If this is the case, this is exactly like doing a Caesar cipher with 1 shift for all of the letters.