Sub Uppercase_Stri()
'In slection, find all instances of the inputboxed string
'and replace them with sequential numbers.

Dim myRng As range
Dim stri As String
Dim i As String

Application.ScreenUpdating = False

Set myRng = selection.range
    stri = InputBox("Enter the string to find")
    i = InputBox("Enter the number to start counting from")
    With myRng.Find
        .ClearFormatting
        .Replacement.ClearFormatting
        .text = stri
        .Forward = True
        .Wrap = wdFindStop
        Do
            If .Execute And myRng.InRange(selection.range) Then
                i = i + 1
                myRng = i
            Else: Exit Do
            End If
            myRng.Collapse
        Loop
    End With
Application.ScreenUpdating = True
Set myRng = Nothing
End Sub