Awk statement to not working for colon symbol

I am working on a AWK script which should replace the value of 3 column from an excel csv sheet to a particular value and the awk should ignore the first and the last line. The problem is with the string i am trying to update is causing issue, Below is the command i am using:

awk -v sq="'" -F, '     t{print t} {a=t=$  0}     NR>2{$  3=sqops_data<dbms=Teradata::instance=idw-prod>sq;t=$  0}     END {print a} ' OFS=, test1.csv 

But, it is giving me syntax error at :: .