DateTime used in Query

Can someone help me out here? I'm basically trying to create a query where I only get records modified in the past (user defined #) of days, but I keep getting an error on my while(queryrun.next()), but no error on compile.

int           modDays;

utcDateTime    myDate;

dataContract = this.parmDataContract();

modDays = dataContract.parmLastModified();

myDate = DateTimeUtil::addDays(DateTimeUtil::getSystemDateTime(),modDays);

tableNum(myTable));

queryBuildRange = queryBuildDataSourse.addRange(fieldnum(myTable, ModifiedDateTime));

queryBuildRange.value(

strFmt('(%1 > "%2")', fieldStr(myTable,ModifiedDateTime), datetime2str(myDate)));

The error I get is Error Executing code: Wrong argument types for comparison.

I know it's something to do with it the type of field, but not sure how to fix?

Thanks!