I would like to run the following 4 sequential models. I would like to create interactions on the fly. How can I include i.var and tell the local macro to pass them to xtreg?

local mod1 = "OTC i.event_date_my"
local mod2 = "`mod1' state_ab#c.event_date_my" // adds state-specific linear time trends
local mod3 = "`mod2' state_ab#(c.event_date_my#c.event_date_my)" // adds quadratic state-specific time trends, and
local mod4 = "`mod3' cov_food_st_person cov_unemp_rate" // the final column adds covariates.

local models "`mod1'" "`mod2'" "`mod3'" "`mod4'"


#delimit ;
foreach dv of local dvs
{;

foreach mod of local models
{;

eststo: quie xtreg `dv' `mod', fe vce(cluster state_ab);
estadd ysumm , mean ; // return only mean
display `dv';
};
};
#delimit cr




---> Stata is complaining at me by throwing this error message: invalid 'i.event_date_my'

Any suggestions? Thank you.