You may optionally change the type of data that are stored by using the drop-down box on the Free Format Variable dialog to change from the default data type (Whole Number) to Decimal or Text.
Example #1: Setting the hidden variable equal to a random number used in the survey.
Suppose you declared a random value earlier in the survey (such as "RandNum(53)") and wanted to store the value of that random number in your data set.
1. Add a Free Format question to your survey and a variable (e.g. myvar1_rand) of type hidden.
2. Edit the HTML (using the "pencil" icon 
and using the Free Format Tools button 
select myvar1_1 from the drop-down control list, to insert the following text in your HTML:
<input name="myvar1_rand" type="hidden">
Then, edit that text to assign the value equal to the function RandNum(53):
<input name="myvar1_rand" type="hidden" value="[%RandNum(53)%]">
Example #2: Setting the hidden variable equal to the sum of two numeric variables on a previous screen. Assume the two previous numeric variables were Value1 and Value2.
1. Add a Free Format question to your survey and a variable (myvar1_sum) of type hidden.
2. Edit the HTML (using the "pencil" icon and select the Free Format Tools button to insert the following text in your HTML:
<input name="myvar1_sum" type="hidden" value="[%Q1+Q2%]">