Bubble Sort: Comparing Numbers & Letters

I have 3 departments, each with a value. I want to sort from lowest value to greatest (which I have done) but some departments won't have a value and therefore will have "n/a" in the place of the value. When sorting, "n/a" always comes out as the greatest value but I want "n/a" to be the lowest value - since it means there is no value.

Here is an example of the data:
Depts: Value:
580 15.75
558 19.01
538 n/a

Here is the code (sorting is being done on the value obviously, and the switching of the Depts to stay with the value is also done in the code)

Private Sub RankPerformance()

Dim bytValuesArrayCount As Byte
Dim A As Byte
Dim B As Byte
Dim vTemp As Variant 'must be type since value can be number or string ("n/a")

bytValuesArrayCount = UBound(ValuesArray)

The only way I know to do it is to sort using the above code, then do another type of sort if a value is not numeric then it is placed at the end...but I'm trying to make the code as efficient as possible