If you set the Text Format property of the textbox to 'Rich Text' it will accept HTML. You can then dynamically insert a bold tag based on the capitalisation in the field, e.g. set control source to:
=IIf(Asc(Left([firstname],1))<91 And Asc(Right([firstname],1))<91,"<b>" & [firstname] & "</b>",[firstname])
Currently this only looks at first and last characters, and you might want to change it so it looks at Ascii values >64 and <91 (so ignores punctuation etc)
