Set range then add values to existing values

I have code the defines a dynamic range then for all cells in that range I want to add the same value but I do NOT want to overwrite the existing numbers. The following code is similar to what I currently have except the range is not dynamic as this is just an example:

Code:

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Sub test()
Dim rng As Range
Dim mynumber As Integer

mynumber = 10
Set rng = Range(Cells(1, 1), Cells(10, 1))

rng.value = mynumber

End Sub

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Obviously this just makes all cells in range rng equal to 10 (overwrites existing values). I also tried:

Code:

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Sub test()
Dim rng As Range
Dim mynumber As Integer

mynumber = 10
Set rng = Range(Cells(1, 1), Cells(10, 1))

rng = rng + mynumber

End Sub

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But just get a "type mismatch" error. I was playing around with some way of copying the existing numbers in the range, pastespecial values somewhere else, then do rng = mynumber then copy/pastespecial add values the original numbers back but this seems a very messy way of doing things. There must be a simple way of just adding to the existing values that I am missing!

Thanks
-Rob

you can do a for each cell in the range

Code:

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For Each c In rng
 c.Value = c + mynumber
Next

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