Maybe you can create a separate column, called c(bis) maybe, that would transform d+e+f into a percentage of c? That's assuming c will vary in each line.
If c stays the same I'm sure you can do it directly as a percentage, although I'll have to find out how, as my memory fails me.
max thanks for the quick response - I have been trying most of the evening to crack this one - never have been that good at formula creation. I have tried the obvious d+e+f/c but I always get the pure % of the one cell. I am completely baffed with this one although it should be quite simple, or so I thought.
Anyone else out there with any bright ideas?