TREND between two points

[Pat Parker]

I have two columns where TREND does not work well. I want to calculate the TREND value of Column 2 (PERCENTILE RANK) based on a new RAW number. If I TREND between just the two rows, the value is fine (i.e. If I TREND between 105 and 110 RAW, I get the right PERCENTILE RANK if the new X value is 106 (which is 15.3% PERCENTILE RANK). How can I make a formula that will only look at the two rows and TREND just those two rows to give me the right PERCENTILE RANK. Thanks in advance!

RAW PERCENTILE RANK
105 14
110 20.4
111 21.8
117 29.5
118 33
123 42.5
124 44.5
129 54.4
130 56.5
135 66.5
136 68.3
142 77.2
143 80.4
148 87.5
149 88
154 93.7
155 94.5
160 97.5
161 97
166 99.2
167 99.3
173 99.8