Option Explicit
 
Private Sub Command1_Click()
    Dim s As String
    Dim start As Long
    Dim ende As Long
 
    s = rtf.Text
    start = 1
    ende = Len(s)
 
    Do
        start = rtf.Find("a", start, ende)
        If start = -1 Then Exit Do
        rtf.SelStart = start
        rtf.SelLength = 1
        rtf.SelColor = RGB(255, 0, 0)
        start = start + 1
    Loop Until start > ende
End Sub
 
Private Sub Form_Load()
    rtf.Text = "xax yay zaz wwwabc a   aaaa   wwwna123"
End Sub

Gru? Michi aus Hannover

1 + 1 = 3 f?r hinreichend gro?e 1