Calculator?

so as mentioned before, (as in a previous thread) i was in the process of making a calculator, i have made one step operation as in X (any operation) X = Y. now in most calculators, you can continue working with the awnser you just got, as in when the text field says a number you can do that number (any operation) (any number), and keep going from there. currently two variables are made, one is the first number and the other is the second, they are distinguished when an operation has been hit, which is a true/false variable. if its true then go to second variable, if false, then go to 1st variable. can someone help me with my problem of contining operation, i would like to avoid using arrays as i do not have any experience with them. this is in visual basic. the computer gets confused with the signHit variable (the true/fase variable that distinguishes if an operation has been hit). i know there are alot of experience logical thinkers on kirupa. please help, i want to get this thing over with,