If cell in range is blank; enter 99999

Ok so it turned out I wasn't on my last question, but hopefully this is.

In the attached sheet, there is a range with lots of entered data (a small section of the total) where I would like to enter into all of the blank cells the value 99999.

I have been selecting the range as follows:

    Sheets("temp").Range("A3").Select
    Sheets("temp").Range(Selection, Selection.End(xlDown)).Select
    Sheets("temp").Range(Selection, Selection.End(xlToRight)).Select

Which is probably not the best, but it works, but need to fill in those gaps?

Many thanks,

Tim