Mike,
Are you saying, "if [MyDescr] is one of 15 value, bold it; otherwise make it un-bold", open your report in design mode, select the report section with that control, and from properties window's Events tab click in the box for the Format event. Two buttons should show up to the right; click the one with '..' select code builder.
You will be moved to the VB Editor. It will start you off with code looking like this:
Code:
Private Sub GroupHeader2_Format(Cancel As Integer, FormatCount As Integer)
End Sub
<swap out GroupHeader2 for the section you selected. Inside those lines, add code like this:
Code:
Select Case Me![MyDescr]
Case "a", "b", "c", "d"
Me![MyDescr].FontBold = True
Case Else
Me![MyDescr].FontBold = False
End Select
Update the code so that the field name matches, and so that the list of values is correct.