I want to know how to transfer the formula of STD ERR OF Prediction of my linear model in Excel. ( std err Pred Formula)

I dont understand it....what is Vec quadratic ?

Formula is: Sqrt(Vec Quadratic([0.615106074605487 -0.05018339188381, -0.05018339188381 0.00428784520440499], [1] || :T20) * 194.153863605514)

T20 is my variable (temperature at 20 cm under surface)

Thank you very much for your answer!