If you do what Ryuji suggests, work in total darkness for the entire operation of re-dying, drying, loading into the film holder (or whatever) and then the dark steps of processing. Be aware that you may encounter drying spots on the film and that the dying process may wash the acutance and AH dyes out of the coating depending on the type of dye already present and the type of solvent you use.
Don't expect stellar results. It may not work.
Being one of the few here that has done spectral sensitization routinely, I am familiar with the pitfalls of this. In fact, I doubt if anyone has done this with really good results.