regular expression for indian land line numbers

 hello everyone i need a regular expression for indian telephone number (land line numbers not mobile number) but note that i have two text boxes one for code which shd allow 3 to 6 digits and 2nd text box which consist of number and ya one label +91 is already there so no need for tat coding
it is like this
+91 (textbox for code) (textbox for phone number)
thanx
 
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