Margin loan to invest and spend

I would like to know if there is a way to separate the margin loan that I get for investing in stocks and the money that I withdraw to pay for expenses like a car. If I deposit more money into my margin account, am I paying the loan that I got to invest or the loan that I withdrew to pay for the car?

I want to differentiate the two cases to request a tax refund of the interest paid to invest in stocks (that generate income). I know that the margin loan to buy a car is not tax deductible.