One way to do this (although it's not foolproof) is to use StrConv function
in code that is run in the AfterUpdate event of the textbox:
Private Sub txtBoxName_AfterUpdate()
Me.txtBoxName.Value = StrConv(Me.txtBoxName.Value, vbProperCase)
End Sub
Note that this will capitalize the first letter of each word, which may not
give the right results for nonstandard names:
rosemarie will become Rosemarie even if it should be RoseMarie
etc.