[RESOLVED] Forced to make an entry in a combobox!

[New2vba]

I've been through this a dozen times and can't seem to work out what's wrong!

I have a combobox (cboGVW), which represents the gross vehicle weight of a truck. The combobox is populated with standard manufacturers weights, but sometimes a custom weight needs to be entered so .matchrequired = false.

I am trying to:

a) Allow numeric or null entries only.
b) Set upper and lower limits for numeric entries.

The code below works in every instance except for allowing null entries! Once the combobox has been selected, I'm stuck there until I enter a valid number!

Private Sub cboGVW_Exit(ByVal Cancel As MSForms.ReturnBoolean)
 
'GVW ENTRY FORMAT VALIDATION
 
    If IsNumeric(cboGVW.Value) And cboGVW.Value >= 7500 And cboGVW.Value <= 32000 Then
        cboGVW.Value = Format(CInt(cboGVW.Value))
    ElseIf IsNumeric(cboGVW.Value) And cboGVW.Value < 7500 Then
        MsgBox "Skiploaders are not suitable for vehicles with a GVW less than 7500kg!" & vbCr & _
        "Please enter a valid GVW or consult Engineering.", vbExclamation + vbOKOnly, "Invalid Entry!"
        cboGVW.Value = Null
        Cancel = True
    ElseIf IsNumeric(cboGVW.Value) And cboGVW.Value > 32000 Then
        MsgBox "Skiploaders are not suitable for vehicles with a GVW greater than 32000kg!" & vbCr & _
        "Please enter a valid GVW or consult Engineering.", vbExclamation + vbOKOnly, "Invalid Entry!"
        cboGVW.Value = Null
        Cancel = True
    ElseIf Not IsNull(cboGVW.Value) Then
        MsgBox "Entries must be numeric and between 7500 and 32000!" & vbCr & _
        "Please enter a valid GVW or consult Engineering.", vbExclamation + vbOKOnly, "Invalid Number Format!"
        cboGVW.Value = Null
        Cancel = True
    Else
    End If
        
End Sub

As usual any help to relieve my pain would be appreciated.

EDIT: Sometimes I should take a step back before I ask! Problem has been resolved, although constructive criticism is always welcome.

Modified Code:

Private Sub cboGVW_Exit(ByVal Cancel As MSForms.ReturnBoolean)
 
'GVW ENTRY FORMAT VALIDATION
 
    If IsNumeric(cboGVW.Value) And cboGVW.Value >= 7500 And cboGVW.Value <= 32000 Then
        cboGVW.Value = Format(CInt(cboGVW.Value))
    ElseIf IsNumeric(cboGVW.Value) And cboGVW.Value < 7500 Then
        MsgBox "Skiploaders are not suitable for vehicles with a GVW less than 7500kg!" & vbCr & _
        "Please enter a valid GVW or consult Engineering.", vbExclamation + vbOKOnly, "Invalid Entry!"
        cboGVW.Value = Null
        Cancel = True
    ElseIf IsNumeric(cboGVW.Value) And cboGVW.Value > 32000 Then
        MsgBox "Skiploaders are not suitable for vehicles with a GVW greater than 32000kg!" & vbCr & _
        "Please enter a valid GVW or consult Engineering.", vbExclamation + vbOKOnly, "Invalid Entry!"
        cboGVW.Value = Null
        Cancel = True
[I]   [B] ElseIf IsNull(cboGVW.Value) Then 'Do nothing[/B]
    [B]Else
        MsgBox "Entries must be numeric and between 7500 and 32000!" & vbCr & _
        "Please enter a valid GVW or consult Engineering.", vbExclamation + vbOKOnly, "Invalid Number Format!"
        cboGVW.Value = Null
        Cancel = True[/B][/I]    
    End If
        
End Sub

EDIT: It's obviously later than I thought - the above doesn't work either!!!