Modules & VBA :: If No Selection Made Show All Values Including Null?

I have a Form with multiple comboboxes and listboxes whose selections are assembled into a query. The combo-box selection goes into an IF-ELSE statement for a selection check (IsNull) and if there is no selection made, it is supposed give me all values (Blanks & Non Blanks)

Here is a sample of my code:

Code:
If IsNull(Me.cbReg.Value) Then
RegStrng = " Like '*'"
Else
RegStrng = Me.cbReg.Value
RegStrng = "= " & RegStrng
End If

I have several If-Else statements here and a final query assembly at the bottom of the code page which is as follows

Code:
MasterSql = "SELECT DISTINCT blah-blah-blah" & _
" INTO some more blah-blah" & _
" FROM even more blah-blah-blah" & _
" WHERE dbo_mytable.[Reg#]" & RegStrng & _
" AND the results from other If-Else statements similar to above"

Here is where the problem comes in:

I see the mistake in my If-Else statement

Code:
If IsNull(Me.cbReg.Value) Then
RegStrng = " Like '*'"

Like * means it will show me all rows where there are NON-Blanks. However, it skips all Blank Data.

What should the If IsNull() statement look like if I want to show all the values?

If there was only one combo-box and there was no selection made, then the resultant query should show me all results rather than only the results where there is some sort of data within the column filtered by the combobox.