I had a question on a test that said to use insoluble compounds to make precipitates to filter out Ca and Ba from solution separately, but I couldn't find anything that will react with one and not the other??
You could carry out the standard qualitative analysis procedure. Dissolve the mixture in hot acetic acid solution.
Then add pottasium chromate ,barium is precipitated as its chromate salt(pale yellow ppt).
Filter it and you could then precipitate Calcium from the resultant filtrate by adding ammonium oxalate.(precipitated as calcium oxalate, white ppt)