-----------------
Function SumC(rng As Range) As String
Dim c As Range
For Each c In rng
SumC = SumC & c
Next
End Function
-----------------

Sub sum()
Dim c As Range
For Each c In Range("E770:E790")
SumC = SumC & c
Next
ActiveCell.Value = SumC
End Sub

Thanks. It works

Another question
I want to select range with mouse instead of ("E770:E790")