This works

Param_2(CR - 2) = (F_Array(CR) - F_Array(CR - 1)) * 100
.Columns(8) = WorksheetFunction.Covar(Param_1, Param_2)
table_aapl1.csv -5.15158E-05
table_abbv.csv -0.002501356
table_abt.csv -0.000789329