I am using the following code in Click property of Combo Box

lcCurDrive = ALLTRIM(Justdrive(Fullpath(Curdir())))
lcCurDir = ALLTRIM(Curdir())

SET DEFAULT TO (sDirectory)
CreateDirectory('Backup',0)
Targetpath='&sDirectory'+'Backup\'
Thisform.unlockallfiles()
Thisform.Fileselect()
Thisform.Unitbackup()
Thisform.circlebackup()
Thisform.Closemonth()
Thisform.lockallfiles()
CHDIR ('lcCurDrive&lcCurDir')

The program Was Running fine, and I was able to come Back to my parent Directory using CHDIR ('lcCurDrive&lcCurDir').
But Suddenly My Program Started throwing error as "Invalid Path" for CHDIR ('lcCurDrive&lcCurDir').

Whats the problem. Kinldy Guide.