I'm still unsure what you're trying to achieve... do you want the message to display the percentage complete in one line only, or display a new line for each percentage complete? Using environment.newline might be what you're after.
using this:
For counter As Integer = 1 To 100
ed.WriteMessage("\n{0}", counter)
Next
i get:
\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\...
using this:
For counter As Integer = 1 To 100
ed.WriteMessage(String.Format("{0}count is {1}", Environment.NewLine, counter))
Next
i get:
count is 1
count is 2
count is 3
count is 4
count is 5
count is 6
count is 7
count is 8
count is 9
count is 10
...
using this:
For counter As Integer = 1 To 100
ed.WriteMessage(String.Format("{0}count is {1}", vbCr, counter))
Next
you'll get a running percentage, but as mentioned previously you'll need to use 'DoEvents' so the command line can be updated