An Option Set control and a Multi line textbox are used to create the Multi Select Checkboxes control. Labels of the checkboxes can be stored in the optionset control as items. Selected values will be saved in the multi line textbox seperated by semi colons.
Control looks like this in the CRM form after implementing it.
Follow the steps below to work with Multi Select Checkbox control.
 Create a OptionSet control and add items to the option set. Items are the checkbox captions in the control.
 Create a Multi line textbox. This will hold all the selected item values.
Download Multi Select Checkboxes Library Here
 Add “OptionSetToMultiSelect.Functions.ToMultiSelect” with relevant parameters to OnLoad event of the form
// Method to be invoked under onload event ToMultiSelect: function (var_sc_optionset, var_sc_optionsetvalue, required, columns)
var_sc_optionset – Name of the option set field
var_sc_optionsetvalue – Name of the multiline textbox
required – Whether the new field(Multi Select Checkboxes control) is required or not
columns – Number of columns to be appeared in the control for checkboxes
 Add “OptionSetToMultiSelect.Functions.CheckAllMultiCheckboxWithLayersRequiredFields” to OnSave event of the form
// Function to be invoked page OnSave CheckAllMultiCheckboxWithLayersRequiredFields: function ()
Thats it! Play with it.