Add data to a column based on other column data

[Fred]

This is what I currently have:

Number Date_tested
5090002 1-Feb-01
5090002 1-May-01
5090002 15-Apr-03
5090034 1-Sep-00
5090034 15-May-01
5090034 15-Apr-03

I need to add the text "Test-1" "Test-2" etc based on the number in the
first column, in other words, when the number in the first column
changes I need the added text to start over at "Test-1"

Number Date_tested Test Number
5090002 1-Feb-01 Test-1
5090002 1-May-01 Test-2
5090002 15-Apr-03 Test-3
5090034 1-Sep-00 Test-1
5090034 15-May-01 Test-2
5090034 15-Apr-03 Test-3

Any ideas?

Thanks!!!
Fred

 

[Fred]

This is what I currently have:

Number Date_tested
5090002 1-Feb-01
5090002 1-May-01
5090002 15-Apr-03
5090034 1-Sep-00
5090034 15-May-01
5090034 15-Apr-03

I need to add the text "Test-1" "Test-2" etc based on the number in the
first column, in other words, when the number in the first column
changes I need the added text to start over at "Test-1"

Number Date_tested Test Number
5090002 1-Feb-01 Test-1
5090002 1-May-01 Test-2
5090002 15-Apr-03 Test-3
5090034 1-Sep-00 Test-1
5090034 15-May-01 Test-2
5090034 15-Apr-03 Test-3

Any ideas?

Thanks!!!
Fred

To claify... there will be different number of tests, so some will have
Test-1 to Test-3 some will have Test-1 to Test-4.... or Test-1 - Test-6