This should work.

WITH oleapp.Selection.Find
.Forward = .t.
.MatchWholeWord = .t.
.MatchCase = .f.
.Replacement.ClearFormatting
.Replacement.Font.Underline = 3
.Text = " Kero: "
.Replacement.Text = " Kero: "
?.execute(" Kero: ") && must be .t. to continue. Your code returns .f. here
ENDWITH
With oleapp.Selection.Font
.Name = "Times New Roman"
.Size = 10
.Underline = .t.
EndWith