I didn't know much about it either, (it's disabled at work, boo hoo), but I thought it would do the trick. Just had a mess around:
Private Sub UserForm_Activate()
rtb.Text = CStr(Date)
With rtb
.SelStart = 0
.SelLength = 2
.SelBold = 1
.SelLength = 0
End With
End Sub
Works fine setting the day to bold on an unbound RTB.
I get the feeling that it is the control source causing the problem. If the control source is incapable of richtext, then I would think that the bound control would also be incapable. Try changing the control source type, failing that, have the bound text box hidden with an on_change event linking it to an unbound richtextbox.
Rather than just waffle, I've tried it in Access.
The controls are basically the problem. I used a date type control and a memo control. Date type simply refused to update the record as the RTB is incompatible with the date control. The memo control cannot handle rich text and therefore converts it all to bold when updated. On first show, it worked fine, and was then all bold.
Two options then:
Use a directly bound field, but unbold everything before you update the datasource.
Or use an unbound RTB and update that from an invisible bound textbox.