Sort The list of items by Alpha / numeric in their proper sequential order

You need to pad the numbers out to constant length, e.g., change P1 to P01, for sorting. Or you could use some formulas:

       --A-- ---B--- -C-- -----D------ -E-- ---F--- -G-- -----H----- -I-- --J--- --K---
   1   PANEL  OPEN        OK TO CLOSED      CLOSED       FINAL INSP.                   
   2         Initial Date   Initial    Date Initial Date   Initial   Date Letter Number
   3   P1                                                                 P           1
   4   P2                                                                 P           2
   5   D11                                                                D          11
   6   P31                                                                P          31
   7   P23                                                                P          23
   8   D2                                                                 D           2
   9   P27                                                                P          27
  10   P30                                                                P          30

J3 and copy down, =LEFT(A3)

K3 and copy down, =--MID(A3, 2, 3)

or use since you only have one leading alpha
=LEFT(A3)&TEXT(RIGHT(A3,LEN(A3)-1),"000")