Welcome to the forums. 
Try this
vb Code:
Private Sub MSFlexGrid1_KeyPress(KeyAscii As Integer)
With MSFlexGrid1
Select Case KeyAscii
Case 8: 'IF KEY IS BACKSPACE THEN
If .Text <> "" Then .Text = _
Left$(.Text, (Len(.Text) - 1))
Case 13: 'IF KEY IS ENTER THEN
Select Case .Col
Case Is < (.Cols - 1):
SendKeys "{right}"
Case (.Cols - 1):
If (.Row + 1) = .Rows Then
.Rows = .Rows + 1
End If
SendKeys "{home}" + "{down}"
End Select
Case Else
.Text = .Text + Chr$(KeyAscii)
'write your own keyascii Validations under
'commented lines
Select Case .Col
Case 0, 1, 2:
'if (your condition(s)) then
'accept only charectors
'Else
' keyascii=0
'End If
Case Else:
End Select
End Select
End With