In my wireframe, I have three variables for numeric input:

DollarAmount1Variable
DollarAmount2Variable
DollarAmount3Variable

Additionally, I have a variable TotalDollarAmountVariable that I'd like to use to display the sums of the above three variables. However, I cannot seem to find a way to add up these values. My hack at doing so was to try setting the TotalDollarAmountVariable to each of the above (see code below). But the result is that it only produces the value for DollarAmount3Variable.

Is there a way to add up variable values?

Here's the code:

Set value of variable TotalDollarAmountVariable equal to value of variable DollarAmount1Variable
     and value of variable TotalDollarAmountVariable equal to value of variable DollarAmount2Variable
     and value of variable TotalDollarAmountVariable equal to value of variable DollarAmount3Variable
     and text on widget TotalDollarAmount equal to "[[TotalDollarAmountVariable]]"

Thanks for your help,

Eric