You just need the result of the entire evaluation to equal "true" so set the parameter to be optional and use the HasValue function and if it returns true, apply it to your field, if not, then return "true" yourself in the "Else" statement.
If HasValue({?ItemCode}) Then
{CI_Item.ItemCode} Like UpperCase("*" + {?ItemCode} + "*") Else
True
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David Speck II
Tennessee Software Solutions
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