How do I perform mathematical operations on GuiXT variables?

GuiXT provides limited support for mathematical computations. The Set command supports the basic operation +,-,*,/. All operands are considered to be numbers. The result is then stored in string format, up to 2 decimal places (rounded) for resulting non-integer values. The format is as follows:

Set V[my_variable] value1 + value2
Set V[my_variable] value1 - value2
Set V[my_variable] value1 * value2
Set V[my_variable] value1 / value2

Note: At least one Space is needed before and after the operator.