combining 2 formulae

I am a beginner in using Excel 2010 and have put together the following formulae, however to get it to work I have had to include an extra column (N5) for calculations.

I am hoping that somebody will help me to rework the formulae to use just the single column (O5) for the combined (N5 )(O5) calculation.

I5= early odds available, If the input value in this field if less than 5 there is no further calculation required, but if the input value is above 5, the N5 place calculation below is triggered:

K5=Result: variable inputs 0,1,2,3 or 4

N5=Place calculation: =IF(K5>0,IF(I5>=5,(I5*100)*20%))

O5=Place Return: =IF(N5=FALSE,-100)*IF(I5=5,K5=0,0)

The reason I have had to use the O5 field is that I was unable to get a minus (-100) value if the K5 value was 0.

I have attached the worksheet.

Thank you in anticipation of some help