Why not use the SolidWorks dimensions?
You can add a dimension and then go to the dimension property dialog box and delete the dimension or you can over ride the dimension, but I wouldn't recommend it.
Welcome to the forum. You posted this in the Drawings and Detailing section, so I assume you're working with a drawing and not a model? Drawing dimensions are generally driven by model dimensions, but if you just want a blank dimension it should be possible to over-ride the dimension text and hit your space bar a few times to display a blank value. Later, when you've entered the correct value in your model you could go back to the Drawing and un-check the Override value box to display the dimension.
Again, this assumes you're working with a Drawing that's referencing a Part or Assembly. If this isn't the case, and you're sketching and dimensioning directly in a SolidWorks drawing, then one way would be to enter a dimension, give it an arbitrary value to fix the line, then hide this dimension and enter a new driven dimension and repeat the process outlined above. When you decide on the final dimensions you could show the original dimension and delete the blank one.
I hope this helps. It's not a workflow I'd normally recommend, but if you really want to show a blank dimension value this should work for you.
I think we are not talking about the same thing. But I did get it to do what I wanted. All I did was add the dimensional lines, enter "T" for text, and then put in a few spaces with the space bar to leave the text blank. Thank you for your help.
At least you gave your self a correct answer