# Using Variables in Formulas

After you add a variable, you can use it in formulas for various system objects (columns, tables, views, etc.). It is important to remember that all variable values are treated by the system as a simple text. Therefore, you cannot simply input variables into formulas that deal with numbers or dates.

When creating formulas with a variable, you will need to convert the variable into a corresponding format. Variables are inserted into formulas in square brackets (for example, Var[hourly rate]). To covert a variable into the necessary format, use the Type Conversion functions ToXXX(Var[variable]), for example:

• ToNumber() used to convert a variable to the number format (for example, ToNumber(Var[hourly rate]));
• ToDate() used to convert a variable to the date format (for example, ToDate(Var[beginning date]));
• ToTimeOfDay() function used to convert a variable to the day time format (for example, ToTimeOfDay(Var[day time])).

When you create a formula, there may occur a situation when a variable and a column have the same name. References to column values and variables are given in formulas in the same way – in square brackets (for example, Var[project start date]). If the names of the column and the variable coincide, the formula will use the column value.

The following table contains examples of converting variables into a different format and using variables in formulas:

 Variable Name Value Format to Convert to Conversion Function Formula Example, Description hourly rate 15.00 Numeric ToNumber(Var[hourly rate]) ToNumber(Var[hourly rate]*8 The formula calculates the amount earned per 8 hours of a normal workday. start date 01-01-2006 Date ToDate(Var[start date]) Today () - ToDate(Var[start date]) The formula calculates how many days have passed from the project start date.