Problem passing a ptr to a fxn into a fxn

I am using the wavelet code from numerical recipes in C.

http://www.library.cornell.edu/nr/bookcpdf/c13-10.pdf

When I try to call a function that calls another function I get the following error in MS Visual C++:

wavelet.obj : error LNK2001: unresolved external symbol "void __cdecl wt1(float *,unsigned long,int,void (__cdecl*)(float *,unsigned long,int))" (?wt1@@YAXPAMKHP6AX0KH@Z@Z)

Debug/w3.exe : fatal error LNK1120: 1 unresolved externals

Error executing link.exe.

The relevant code is as follows:

void daub4(float *, unsigned long, int);

void wt1(float *, unsigned long, int, void (*)(float [], unsigned long, int));

void main(){

...

wt1(x, numPoints-1, 1, daub4);

...

}

void wt1(float a[], unsigned long n, int isign,

float(*wtstep)(float [], unsigned long, int)){

//One-dimensional discrete wavelet transform. This routine implements the pyramid algorithm,

//replacing a[1..n] by its wavelet transform (for isign=1), or performing the inverse operation

//(for isign=-1)

//. Note that n MUST be an integer power of 2. The routine wtstep, whose

//actual name must be supplied in calling this routine, is the underlying wavelet .lter. Examples

//of wtstep are daub4 and (preceded by pwtset) pwt.

unsigned long nn;

if (n < 4) return;

if (isign >= 0) { //Wavelet transform.

for (nn=n;nn>=4;nn>>=1) (*wtstep)(a,nn,isign);

//Start at largest hierarchy, and work towards smallest.

} else { //Inverse wavelet transform.

for (nn=4;nn<=n;nn<<=1) (*wtstep)(a,nn,isign);

//Start at smallest hierarchy, and work towards largest.

}

}

void daub4(float *a, unsigned long n, int isign){

.......

.......

}

Please help me to pass daub4 into wt1!

Thanks,

*Bob_ptr