This is my data (5 columns). I have a custom format on it (##+##.00). I am
trying to get a formula to add values at 50 feet before the first value in
the row, 50 feet after each value in the row until it reaches the next value
then repeat, and 50 feet after the ending value in the row (the new rows of
data are being placed out beside the old data). I have tried for two days
everything I know to do, and I can't get it to work. Below the data are the
last formulas that I have written (One is for the first cell, and the other
is for the following cells). I could really use some help. Thanks.

20+83.25 23+83.25 24+48.23 25+11.02 28+11.02
43+49.91 45+49.91 46+08.68 46+64.08 48+64.08
50+58.42 52+08.42 52+12.44 52+15.80 53+65.00
68+36.40 71+36.40 72+29.87 73+20.29 76+20.29
86+35.30 88+85.30 89+58.95 90+15.30 92+65.30
106+88.10 109+88.10 110+57.15 111+17.27 114+17.27
121+53.22 124+03.22 126+39.39 128+33.55 130+83.55
144+60.21 146+60.21 146+98.18 147+32.09 149+32.09
158+44.44 161+44.44 161+80.12 162+09.92 165+09.92
174+33.17 176+83.17 177+70.58 178+47.46 180+97.46
199+11.35 201+11.35 201+37.01 201+59.47 209+65.54
203+89.04 205+89.04 206+85.26 207+65.54 209+65.54
211+82.95 215+82.95 217+68.98 218+98.78 222+98.78
238+54.52 242+04.52 242+63.69 243+15.02 246+65.02

=ROUNDDOWN(D3,-2)

=IF(AND(($D$3-R3)<50,($D$3-R3)0), $D$3, IF(AND(($E$3-R3)<50, ($E$3-R3)0),
$E$3, IF(AND(($G$3-R3)<50, ($G$3-R3)), $G$3, IF(AND(($I$3-R3)<50, ($I$3-R3)),
$I$3, IF(AND(($J$3-R3)<50, ($J$3-R3)), $J$3, MROUND(R3,(R3+50)))))))