According to most contemporary scholars and AAOIFI, if a Murabaha transaction is constructed around a variable profit rate, then this will not be permissible.
This is due to the element of uncertainty present in such agreement.
Dr Yusef Al Shubaily is of the opinion that such agreement is allowed since there is no proof for its prohibition in the Islamic jurisprudence.
And Allah knows best!
(Mufti) Billal Omarjee