I want put right headed double arrow between first two columns of the table

My code:
\documentclass[12pt,a4paper]{article}
\usepackage{algorithmic,algorithm,amsmath} %for mathematics %
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{booktabs}
\usepackage{array}
\usepackage{paralist}
\usepackage{bigstrut}
\usepackage{multirow}
\usepackage{dcolumn}
\begin{document}
\newcolumntype{d}[1]{D{.}{.}{#1}}
{\setlength{\extrarowheight}{1.5pt}
\setlength{\tabcolsep}{1pt}
\begin{table}[htbp]
\centering
\caption{The Results of Granger and MWALD tests}
\begin{tabular}{llccccc}
\toprule
\multirow{2}[4]{*}{Null Hypothesis} & \multicolumn{2}{c}{Grangers’ test (Short run)} & & \multicolumn{2}{c}{MWALD test (Long run)} \\
\cmidrule(r){3-4} \cmidrule(r){6-7}
\multicolumn{1}{l}{} & \multicolumn{1}{l}{} &\multicolumn{1}{c}{F-Statistics} &\multicolumn{1}{c}{p-values} & &\multicolumn{1}{c}{$\chi^{2}$-Statistics} & \multicolumn{1}{c}{p-values} \\
\midrule
\multicolumn{1}{l}{LTC} & \multicolumn{1}{l}{LGDP} & 7.736** & 0.021 & & 0.169 & 0.919 \\
\multicolumn{1}{l}{LGDP} & \multicolumn{1}{l}{LTC} & 0.504 & 0.777 & & 1.763 & 0.414 \\
\multicolumn{1}{l}{LCO2} & \multicolumn{1}{l}{LGDP} & 10.829* & 0.005 & & .324 & & 6.490 & 0.039 \\
\multicolumn{1}{l}{LCO2} & \multicolumn{1}{l}{LCC} & 10.673* & 0.014 & & 7.378** & 0.025 \\
\bottomrule
\end{tabular}%
\label{tab:addlabel}%
\end{table}%
\end{document}

!in front of it to turn it into a link. A moderator or another user with edit privileges can then reinsert the!to turn it into an image again (ad I did). It is better to turn your code snippet into a (MWE) starting with\documentclassending with\end{document}and including only the necessary packages. This will help who wants to answer you.:)– Claudio Fiandrino Mar 30 '13 at 10:08\multicolumn-command to check its first argument, and if it equals1, it would delete itself from the source file. – morbusg Mar 30 '13 at 10:39\\[\medskipamount]instead of just\\\. – morbusg Mar 30 '13 at 10:57==>but your table would probably look better if the numerical columns aligned on.you declare a decimal alignment column type but don't use it? – David Carlisle Mar 30 '13 at 12:10