I assume you count Sunday as the only non-workday
Assuming start date in A2, workdays to add in B2, list of holiday dates
defined as named range holidays
=A2+SMALL(IF((WEEKDAY(A2+ROW(INDIRECT("1:"&B2*10)))>1)*ISNA(MATCH(A2+ROW(INDIRECT("1:"&B2*10)),holidays,0)),ROW(INDIRECT("1:"&B2*10))),B2)
confirmed with CTRL+SHIFT+ENTER
format as date