Beginner – Crystal Report and VB – Help needed

Hai,
I am using vb6 and crystal report 8.5. I want to pass a parameter to the crystal report from VB. I used the following code from a book I referred. But it shows syntax error. Pl.guide me.

crystalreport1.selectionformula=”{servmst.mrtcd}='”&wmrtcd&”‘”

wmrtcd is the variable at run time for the parameter.