Adding % to a Range of Prices???

[thelawns]

Ok, I have a requirement to add a certain % to a range of prices. I'm obviously going to have to decide on a few certain key points. For example from 1p to £5 with a varying % increase:

0.01 to 0.50 = 300%
0.51 to 1.00 = 250%
1.01 to 1.50 = 200%
1.51 to 2.00 = 180%
2.01 to 2.50 = 160%
2.51 to 3.00 = 140%
3.01 to 3.50 = 120%
3.51 to 4.00 = 100%
4.01 to 4.50 = 90%
4.51 to 5.00 = 80%

Basically, I need it to output the % at, for example £4.30, at the exact % in the curve, so it wouldn't be 90% exactly? It would be somewhere between 100% and 90%?

Would it be simpler to look at the range this way?

< £0.50 = 300%
< £1.00 = 250%
< £1.50 = 200%
< £2.00 = 180%
< £2.50 = 160%
< £3.00 = 140%
< £3.50 = 120%
< £4.00 = 100%
< £4.50 = 90%
< £5.00 = 80%

Basically, based on a flat spreadsheet, a costing of 4.49 would add more % than a costing of 4.50. I need it to be less by the appropriate % less based on the curvature of a graph I suppose?

Is it something to do with VLOOKUP command ??

I have been playing with this for days now. I just can't get my head around it so I have found this site and i'm hoping some of you guys or gals may be able to help!

Thanks