Option Explicit
Const MaColonne = "A"
Const Mafeuille = "Test"
Sub PremLettre()
Dim xcell
Application.ScreenUpdating = False
With Sheets(Mafeuille)
For Each xcell In Intersect(.Range(MaColonne & ":" & MaColonne), .UsedRange)
With xcell.Characters(Start:=1, Length:=1).Font
.FontStyle = "Gras"
.Color = RGB(255, 0, 0)
End With
Next xcell
End With
End Sub