Setting Query Search Criteria From A Form

Looking to be pointed in the corect direction,

having trouble using a text box on a form to set the search criteria for a particular field within a query.

Ideally i would like to enter the criteria in a textr box then click a button which sets the criteria and opens the query results in a report,

I have designed the query but cant which works if you go into the design and enter the criteria. the problem lies with getting the text box on teh form to set teh criteria.

If i use the expression builder to set the criteria to the same value of the "text" within the "text box" on said form the following happens,

If i open the query itself it opens a small window and displays the "expression" that i entered in the criteia box, above the data entry. the query does work this way but dont understand why the expression is displayed???
The text box on the form also becomes locked, not allowing data to be entered.

I have tried to link the query direct to the text box.
also tried creating a table which has data entered via form then linking the query criteria to a field in the table.

Could some one point me in the right direction please

many thanks

Cheers

watson