Constant to display the Percentage inn ssrs 2008

I don't declare constant values in my query suppose 109 and 45,but i use an expression to display my constant value's, I have another column which display the percentage for 2 column fields. the column for my constant and  the total for the type fields.my question if i display the percentage for each two columns fields will it works if i write my constant as expression but not in query.