Here's a simpler way to achieve the same result

DECLARE
	@expr 		nvarchar(100),
	@sql 		nvarchar (200),
	@yUsaAmt 	money,
	@ySpecialChrg 	money,
	@ySpecialDisc 	money,
	@yResult 	money;
	
--SET @expr = N'(@yUsaAmt * 0.05) + @ySpecialChrg - @ySpecialDisc';
--SET @expr = N'(@yUsaAmt * 0.05) + @ySpecialChrg';
SET @expr = N'(@yUsaAmt * 0.05)';

SET @yUsaAmt 	  = 150.00;
SET @ySpecialChrg = 3.00;
SET @ySpecialDisc = 1.75;

SET @sql = N'SET @yResult = ' + @expr;

EXECUTE sp_executesql @sql, 
		N'@yUsaAmt money, @ySpecialChrg money, @ySpecialDisc money, @yResult money OUTPUT',
		@yUsaAmt, @ySpecialChrg, @ySpecialDisc, @yResult OUTPUT;

SELECT @yResult;  

>Perfect!
>I will use it.
>Thanks.
>