Sorry for the confusion. I would like to specify the full pressure profile on the boundary, not just a single value. 

Preferably, I want to try and avoid doing interpolation inside the solver to reduce the compute time (and so that I'm sure of the interpolation method). I'm happy to do my own interpolation so that the file I read in will have the exact data for each cell. Then I hope to organise the data in such a way that it is in the same order as the cells are stored in Fluent.