Hydro-logic data Interpolation en Excell 2007

I have some excel Hydrologic data. But there are some missing data. I want to find what is the procedure od data interpolatiion. Please help me.
Distance Elevation
100 2
110 -2
120 -3
130 4
140 5
150 -6
160 7
170 -8
180
190
200
210
220
230 -2
240 1
250 3
260 -2
270 1