Error in table lookup

I am trying to lookup a value in 1 of 10 loaded two column-data sets (Bins)
by displaying the value of the second column based on the value of the
first. For instance in 

 Bin1_Acres       Bin1_parprob    Bin1_TAZ 
 [1,]   0.000442    0.9999978      356           
 [2,]   0.000453    0.9999954      356          
 [3,]   0.000583    0.9999925      366          
 [4,]   0.000635    0.9999893      403           
 [5,]   0.000756    0.9999854      358           
 [6,]   0.000774    0.9999815      530           
 [7,]   0.000813    0.9999773      405           
 [8,]   0.000970    0.9999724      576           
 [9,]   0.001022    0.9999672      569       
[10,]   0.001066    0.9999618      620         

I would like to display the column value on Bin1_parprob based on the
closest match to Bin1_acres.  So if the value i am referenceing in column 1
(Bin1_Acres) is .009999 the value outputted would be .9999672.   I keep
getting a numeric(0) error with the code i am using(see below).  I think the
issue is i usually dont have an exact match and i am using a >= sign which
may be causing the problem.   I need the closest match and it needs to be
larger, not smaller if not exact match is found( which is very common).  

#Test value for Vacant acres in TAZ 
TAZDetermine = 24

#Test value for and development size
Dev_Size= 3.5

#Determines Bin number based on vacant acres in TAZ
BinSize=function(Dev_Size,BinNumer){
if (TAZDetermine<=3.999)
	BinNumber=1
if (TAZDetermine>=4:6.999)
	(BinNumber=2)
if (TAZDetermine >=10:16.999)
	(BinNumber=3)
if (TAZDetermine>=17:27.999)
 	(BinNumber=4)
if (TAZDetermine>=28:49.999)
 	(BinNumber=5)
if (TAZDetermine>=50:90.999)
 	(BinNumber=6)
if (TAZDetermine>=91:150.999)
 	(BinNumber=7)
if (TAZDetermine>=151:340.999)
 	(BinNumber=8)
if (TAZDetermine>=341:650.999)
 	(BinNumber=9)
if (TAZDetermine>=651:3000)
 	(BinNumber=10)
BinNumber
}

#so in this case Bin 4 is selected

#Based on previously selected bin, display second column
value(Bin1_parprob).  Selected value in column 1 may be slightly larger but
closest match is desirable.   

if (BinNumber==1)
	(Loc_Prop=Bin1Main.data[Bin1Main.data$Bin1_Acres >=Dev_Size,1])
if (BinNumber==2)
	(Loc_Prop=Bin2Main.data[Bin2Main.data$Bin2_Acres>=Dev_Size,1])
if (BinNumber==3)
	(Loc_Prop=Bin3Main.data[Bin3Main.data$Bin3_Acres>=Dev_Size,1])
if (BinNumber==4)
	(Loc_Prop=Bin4Main.data[Bin4Main.data$Bin4_Acres>=Dev_Size,1])
if (BinNumber==5)
	(Loc_Prop=Bin5Main.data[Bin5Main.data$Bin5_Acres>=Dev_Size,1])
if (BinNumber==6)
	(Loc_Prop=Bin6Main.data[Bin6Main.data$Bin6_Acres>=Dev_Size,1])
if (BinNumber==7)
	(Loc_Prop=Bin7Main.data[Bin7Main.data$Bin7_Acres>=Dev_Size,1])
if (BinNumber==8)
	(Loc_Prop=Bin8Main.data[Bin8Main.data$Bin8_Acres>=Dev_Size,1])
if (BinNumber==9)
	(Loc_Prop=Bin9Main.data[Bin9Main.data$Bin9_Acres>=Dev_Size,1])
if (BinNumber==10)
	(Loc_Prop=Bin10Main.data[Bin10Main.data$Bin10_Acres>=Dev_Size,1])

I hope this question is clear.  I have tried a number of different lines of
code but get the same error (Numeric (0))  
Cheers, 
JR