Write some Software

I am looking for a software tool to help me with the below project. I have looked at some CAD software and it is way too complicated and expensive since I only need a basic programme that includes only 3 different size concrete blocks with no background or any other requirement. Basically, it would be great to have some sort of ‘CAD for idiots’ programme written just for the placement of our blocks. The programme would just need the three sizes of blocks we do included and my vision is to be able to draw the basic outline of the structure and add the length of each wall and the overall height and the programme works out what blocks I need per level to ensure all the walls interlock together. The Lego like block sizes are as follows and a picture is attached. Full block - 1500mm x 600mm x 600mm with 2 rows of 5 interlocking nodules Mid block - 900mm x 600mm x 600mm with 2 rows of 3 interlocking nodules Small block 600mm x 600mm x 600mm with 2 rows of 2 interlocking nodules This visualisation will then be used by our haulier as a laying pattern and by me for quoting and ordering purposes. Currently I do this on graph paper but it is not the best solution and is time consuming. I don’t want anything fancy, it’s got to be simple to use. Attached is pictures of some of the uses for our blocks and a diagram of how I normally have to work the blocks out