userform and data entry help

I have attached my spreadsheet I am working on.

Basically I want the spreadsheet to have a window pop up when "Standby" is entered into the "activity" column. The pop up would then have a couple buttons either "Weather Related" or "Client Related" when the user picks one, the data from column C "Unit Install hours" is transferred to the appropriate column either J or K.

J and K will be hidden to the user, I don't want to confuse the data entry people.

Is this the easiest way to do it?

In other words I want to break down what standby means without having a million columns the data entry people will have to go through because all of the activities will have sub activities.

Thanks!