can anyone help me for NSIS Script I have a case where I need to check cases can be 3.3 3.42 23.5 23.56w 3.467 999.999 999.99a but not 1.b or 8..a

Question

This script checks that: The version string is at least 3 characters long. The version string is not blank. The version contains a period. The characters before . Are digits. All characters except possibly the last are digits or a period. The last character after . is a digit or a letter.(digit at last of number) If conditions are not working in the problem

${If} $sVersion == ""
    MessageBox MB_OK "You can't leave Version blank"
    Abort
${EndIf}
    StrCpy $R1 $sVersion
    Strlen $R2 $R1
    ${If} $R2 < 3
          MessageBox MB_OK "Version must be atleast 3 characters long including a period ."
          Abort
    ${EndIf}
    ${StrContains} $R0 $R1 "."
    ${If} $R0 == -1
             MessageBox MB_OK "Version must contain a digit"
             Abort
    ${EndIf}
    StrCpy $R3 0
    loop:
         StrCpy $R4 $R1 1 $R3
         ${If} $R4 == "."
               Goto checkLastChar
         ${EndIf}
         ${If} $R4 < "0"
               ${OrIf} $R4 > "9"
                       MessageBox MB_OK "All Characters Before the Period . must be a digit"
                       Abort
         ${EndIf}
         IntOp $R3 $R3 + 1
         StrCmp $R3 $R0 loop
    checkLastChar:
          StrCpy $R5 $R1 1 $R2
          ${If} $R5 < "0"
                ${OrIf} $R5 > "9"
          ${AndIf} $R5 < "a"
                ${OrIf} $R5 > "z"
          ${AndIf} $R5 < "A"
                ${OrIf} $R5 > "Z"
                        MessageBox MB_OK "The last character must be a digit or a letter"
                        Abort
          ${EndIf}
    end_loop:

FunctionEnd