Sub Boldit
do
With Selection.Find
    .Text = "abc"
    .Format = False
    .Wrap = wdFindStop
    If .Execute Then
        ActiveDocument.Tables(1).Rows(1).Range.Select
 Selection.Font.Bold = wdToggle
    End If
End With
Loop While Selection.Find.Found
End Sub

Hi ldh,

You might want to try the following:

With Selection.Find
    .Text = "abc"
    .Format = False
    .Wrap = wdFindStop
    Do While .Execute
        ActiveDocument.Tables(1).Rows(1).Range.Font.Bold = wdToggle
    Loop
End With

Each time you select the row, you might be placing the cursor before the
first occurence of "abc" and therefore creating an infinite loop.

HTH