How you test depends on the Property's DataType:

| Type                                 | Test                            | Test2
| Numeric (Long, Integer, Double etc.) | If obj.Property = 0 Then        | 
| Boolen (True/False)                  | If Not obj.Property Then        | If obj.Property = False Then
| Object                               | If obj.Property Is Nothing Then |
| String                               | If obj.Property = "" Then       | If LenB(obj.Property) = 0 Then
| Variant                              | If obj.Property = Empty Then    |

You can tell the DataType by pressing F2 to launch the Object Browser and looking up the Object. Another way would be to just use the TypeName function:MsgBox TypeName(obj.Property)

Depends what you are testing.

A range object or a cell value?

Sub test()

Dim rngObject As Range
Dim value As Variant

    Set rngObject = Sheet1.Range("A1:D5")

    If Not rngObject Is Nothing Then
    'If not nothing then run this code
    End If

    value = rngObject.Cells(1, 1).value
    If Not IsEmpty(value) Then
    'if Not empty then run this code
    End If

    If value <> vbNullString Then
    'if value is not nullstring then run this code
    End If


End Sub

Use Not IsEmpty().

For example:

Sub DoStuffIfNotEmpty()
    If Not IsEmpty(ActiveCell.Value) Then
        MsgBox "I'm not empty!"
    End If
End Sub

You have many way to do that like below :

Dim StrFiles As String
StrFiles = Trim(StrFile1 & StrFile2)

If IsEmpty(StrFiles) Then
If StrFiles = vbNullString Then
If StrFiles = "" Then
If StrFiles = Empty Then
If Len(StrFiles) = 0 Then

you can use + operator to check 2 strings are empty reference to your code, because Len Function returns an integer containing either the number of characters in a string

If (Len1 + Len2) = 0 Then