Code:
SqlStr = "UPDATE Table1 SET field1= '"+Var1+"' , Field2 = "'+Var2 + "' , Field3 = '" +Var3 +"' WHERE field1 = '"+CtrlVar+"'"
SQL Syntax For Update ( SEE Transact-SQL Guide For Detailed SQL Syntax

UPDATE {table_name | view_name}
SET [{table_name | view_name}]
{column_list
| variable_list
| variable_and_column_list}
[, {column_list2
| variable_list2
| variable_and_column_list2}
... [, {column_listN
| variable_listN
'
|variable_and_column_listN}]]
[WHERE clause]