Modules & VBA :: Combo Box Does Not Want To Change Background Color

I have some code to check a combo box if a date field is filled in, then the combo box can't be empty.I can make the error message appear, but the combo box does not want to change color and it does not recognize any other than value..This is the code that I have, and it does not work like I wish it could.(I took the database over from some one else and need to make improvements on it. the field names where not created by me).

Code:
Private Sub cmbCurrentStatus_AfterUpdate() '<<<<<<<<<<<<<<<< Working on >>>>>>>>>>>>>
If IsNull(Me.[STEP 1 4 check current status]) And Not IsNull(Me.[Checked__date_]) Then
MsgBox "Checked (date) can't be empty if Current Status is filled in!", , "Incomplete Form!"
Me.[STEP 1 4 check current status].Value = RGB(255, 0, 0)
Else
Me.[STEP 1 4 check current status].BackColor = RGB(255, 255, 255)
End If
End Sub