If statement not recognising a combo box

[JoseSharp]

Hi, I have an if statement that dose not recognise if a combo box is blank or not. There are three types of code that I have tried:

If !F34 = 0 And !Report = "Domestic" Then
If !Combo70 Is Null Then

If !F34 = 0 And !Report = "Domestic" Then
If !Combo70 = Null Then

If !F34 = 0 And !Report = "Domestic" Then
If !Combo70 = 0 Then

Anyone any ideas why !Combo70 code is not recognised when !Combo70 = Null at the time of running the code??

 

[RuralGuy]

If IsNull(!Combo70) Then
or
If Len(!Combo70 & "") = 0 Then

 

[JoseSharp]

Excellent thanks!!!

 

[RuralGuy]

Glad I could help.