Here is the code that I have:
<SPAN class="keyword token">import</SPAN> arcpy
<SPAN class="comment token"># uses the mxd that is running this code</SPAN>
mxd <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>MapDocument<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"CURRENT"</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="comment token"># df is the dataframe, Layers is used to run through all the layers within the mxd. Leave Layers as is</SPAN>
df <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>ListDataFrames<SPAN class="punctuation token">(</SPAN>mxd<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"Layers"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN>
<SPAN class="comment token"># lyr sets the layer, needs to be spelt exactly as the layer sits in ArcMap</SPAN>
lyr <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>ListLayers<SPAN class="punctuation token">(</SPAN>mxd<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"PARCELS.PARCELS"</SPAN><SPAN class="punctuation token">,</SPAN> df<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>env<SPAN class="punctuation token">.</SPAN>overwriteOutput <SPAN class="operator token">=</SPAN> <SPAN class="token boolean">True</SPAN>
<SPAN class="comment token"># sets the parameters, this must be setup in the toolbox script</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>AddMessage<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"Workspace added"</SPAN><SPAN class="punctuation token">)</SPAN>
FClass <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>GetParameterAsText<SPAN class="punctuation token">(</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">)</SPAN>
Field <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>GetParameterAsText<SPAN class="punctuation token">(</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">)</SPAN>
Feature <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>GetParameterAsText<SPAN class="punctuation token">(</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="comment token"># sets the Feature parameter equal to the user input string</SPAN>
where_clause <SPAN class="operator token">=</SPAN> <SPAN class="string token">"""{} = '{}'"""</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>arcpy<SPAN class="punctuation token">.</SPAN>AddFieldDelimiters<SPAN class="punctuation token">(</SPAN>FClass<SPAN class="punctuation token">,</SPAN> Field<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">,</SPAN>
Feature<SPAN class="punctuation token">)</SPAN> <SPAN class="comment token"># I have added extra pair of single quotes for selecting strings</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>AddMessage<SPAN class="punctuation token">(</SPAN>where_clause<SPAN class="punctuation token">)</SPAN>
<SPAN class="comment token"># selects the attribute using the string the user input</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>SelectLayerByAttribute_management<SPAN class="punctuation token">(</SPAN>lyr<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"NEW_SELECTION"</SPAN><SPAN class="punctuation token">,</SPAN> where_clause<SPAN class="punctuation token">)</SPAN>
<SPAN class="comment token"># zooms to selected feature</SPAN>
df<SPAN class="punctuation token">.</SPAN>zoomToSelectedFeatures<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>AddMessage<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"All done!"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="line-numbers-rows"><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN></SPAN>My parameters are as follows:
InputFeatureClass = Data Type: Feature Class, Required, Input, No Multivalue, Default: Database Connections\Connection to gis.sde\PARCELS
InputField = Data Type: Field, Required, Input, No Multivalue, Obtained from Input Feature Class
InputValue = DataType: String, Required, No Multivalue
Thank you everyone for your help!