how to define variable in ssh

I need to use ssh to send command to different computers to run programs. Can I define a variable of Directory and program in front of this shell script? Then, I do not need to write them every time?

host_list=("c15-0330-10.ad.mtu.edu" "c15-0330-11.ad.mtu.edu" "c15-0330-12.ad.mtu.edu") # I have multiple programs # program=c("L_1","L_2","L_3") ssh -f "${host_list[0]}" 'set Directory="/home/campus27/zwang10/Desktop/AWRR/program/power/vmodel_1/nprot/K_10"; cd $Directory && nohup Rscript L_1.R> L_1_sh.txt;echo "The job L_1 is finished" |mutt "zwang10@mtu.edu" -s "The job L_1 is finished"'; ssh -f "${host_list[1]}" 'set Directory="/home/campus27/zwang10/Desktop/AWRR/program/power/vmodel_1/nprot/K_10"; cd $Directory && nohup Rscript L_2.R> L_2_sh.txt;echo "The job L_2 is finished" |mutt "zwang10@mtu.edu" -s "The job L_2 is finished"'; ssh -f "${host_list[2]}" 'set Directory="/home/campus27/zwang10/Desktop/AWRR/program/power/vmodel_1/nprot/K_10"; cd $Directory && nohup Rscript L_3.R> L_3_sh.txt;echo "The job L_3 is finished" |mutt "zwang10@mtu.edu" -s "The job L_3 is finished"';