Your compiler/linker is just saying that it can't find the function "XLCDDelay4ms" anywhere (in the object files you used, or in the library you're pulling in during the link phase).
1) make sure the function name is correct, ie no typographical errors
2) try to find who find the definition of "XLCDDelay4ms" in your source and check if it is being conditionally compiled, ie the code is inside a #ifdef
HTH