Preventing Blank Spaces On Userform Textboxes

On a userform, I have three textboxes, one listbox, and an OK button. When the user presses the OK button, the information in these boxes is pasted onto a worksheet. I am wondering how I can detect if any of these boxes have been accidentally left empty, so as to prevent the user from pasting an incomplete entry onto the worksheet. This is what I have so far (this is part of the routine that executes when the OK button is pressed):

If EnterGrowerTextBox.Text = "" Then
MsgBox "Please Enter the Grower Name"
Exit Sub
End If
If EnterAmountTextBox.Text = "" Then
MsgBox "Please Enter the Number of Chicks"
Exit Sub
End If
If EnterBreedTextBox.Text = "" Then
MsgBox "Please Enter the Breed"
Exit Sub
End If......................