Drop Down Selection Box

[dgrimm]

I am creating a user form and need to catch if the person entering the values skips over one of the areas. I have the simple list box checks in place with an if blah = "" then inputbox blah.
But I have some combo/drop down boxes also that I am needing to check the same way but can not figure out how to have a combobox/drop down box pop up if the initial value is blank.

If EffDteTxt = "" Then Sheets("Sheet1").Range("L7").Value = InputBox("The Effective Date is blank, Please enter the Effective Date") - this is a simple list box and this works.
If CubJobCB = "" Then Sheets("Sheet1").Range("C18").Value = - this is the drop down that I am having trouble figuring out the code for.

Is this even possible to create a if then statement to have a drop down pop up like the input box line??

Thanks Dave