If you're using a text box it would probably be just as easy as:
Code:
Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
If KeyCode = vbKeyReturn Then
If txtType.Text = "" Then
txtType.SetFocus
Else
picScreen.SetFocus
End If
End If
Call CheckInput(1, KeyCode, Shift)
End Sub
Of course, txtType is the name of my text box, so you'll need to make the necessary changes. Anyways, what this will do is check if the enter key was hit. if so, it then checks of there is no text typed into the text box it sets the focus to the text box, allowing you to begin typing. If there is text already in the text box, it sets the focus back to picScreen, "deselecting" the text box, so the user will not be able to type until the text box is cleared. Each time, no matter the outcome, it calls the checkinput sub so it can still do the necessary checks for picking up items etc. It might not work that flawlessly, but try it out, see what happens.
Also, I should add that if you wanted something like world of warcraft for instance, where the text box is hidden until enter is pushed, then you would just put that in there as well as an additional check, like fox described above.
There's really a million possibilities when it comes to how your players will enter text. This should get you started though.