function addConditionalFormatting() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheetByName("Sheet3");
var range = sheet.getRange("A2:C");
var rule = SpreadsheetApp.newConditionalFormatRule()
.whenTextEqualTo("TRUE")
.setBackground("#EFEFEF")
.setFontColor("#CCCCCC")
.setStrikethrough(true)
.setRanges([range])
.build();
var rules = sheet.getConditionalFormatRules();
rules.push(rule);
sheet.setConditionalFormatRules(rules);
var sheet4 = ss.getSheetByName("Sheet4");
var range4 = sheet4.getRange("A2:C");
var rule4 = SpreadsheetApp.newConditionalFormatRule()
.whenTextEqualTo("TRUE")
.setBackground("#EFEFEF")
.setFontColor("#CCCCCC")
.setStrikethrough(true)
.setRanges([range4])
.build();
var rules4 = sheet4.getConditionalFormatRules();
rules4.push(rule4);
sheet4.setConditionalFormatRules(rules4);
}